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Enhance readability of N Queens #9265

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a1853d6
Enhance readability of N Queens
Hardvan Oct 1, 2023
631a3ce
Simplify is_safe code
Hardvan Oct 1, 2023
93937d4
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Oct 1, 2023
374faca
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tianyizheng02 Oct 22, 2023
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53 changes: 26 additions & 27 deletions backtracking/n_queens.py
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -17,50 +17,49 @@ def is_safe(board: list[list[int]], row: int, column: int) -> bool:
This function returns a boolean value True if it is safe to place a queen there
considering the current state of the board.

Parameters:
board(2D matrix) : board
row ,column : coordinates of the cell on a board
Parameters:
board(2D matrix): The chessboard
row, column: Coordinates of the cell on the board

Returns:
Returns:
Boolean Value

"""
for i in range(len(board)):
if board[row][i] == 1:
return False
for i in range(len(board)):
if board[i][column] == 1:
return False
for i, j in zip(range(row, -1, -1), range(column, -1, -1)):
if board[i][j] == 1:
return False
for i, j in zip(range(row, -1, -1), range(column, len(board))):
if board[i][j] == 1:
return False
return True

n = len(board) # Size of the board

# Check if there is any queen in the same row, column,
# left upper diagonal, and right upper diagonal
return (
all(board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, n)))
and all(
board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, -1, -1))
)
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, n)))
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, -1, -1)))
)


def solve(board: list[list[int]], row: int) -> bool:
"""
It creates a state space tree and calls the safe function until it receives a
False Boolean and terminates that branch and backtracks to the next
This function creates a state space tree and calls the safe function until it
receives a False Boolean and terminates that branch and backtracks to the next
possible solution branch.
"""
if row >= len(board):
"""
If the row number exceeds N we have board with a successful combination
If the row number exceeds N, we have a board with a successful combination
and that combination is appended to the solution list and the board is printed.

"""
solution.append(board)
printboard(board)
print()
return True
for i in range(len(board)):
"""
For every row it iterates through each column to check if it is feasible to
For every row, it iterates through each column to check if it is feasible to
place a queen there.
If all the combinations for that particular branch are successful the board is
If all the combinations for that particular branch are successful, the board is
reinitialized for the next possible combination.
"""
if is_safe(board, row, i):
Expand All@@ -77,14 +76,14 @@ def printboard(board: list[list[int]]) -> None:
for i in range(len(board)):
for j in range(len(board)):
if board[i][j] == 1:
print("Q", end=" ")
print("Q", end=" ") # Queen is present
else:
print(".", end=" ")
print(".", end=" ") # Empty cell
print()


# n=int(input("The no. of queens"))
# Number of queens (e.g., n=8 for an 8x8 board)
n = 8
board = [[0 for i in range(n)] for j in range(n)]
solve(board, 0)
print("The total no. of solutions are:", len(solution))
print("The total number of solutions are:", len(solution))
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Enhance readability of N Queens by Hardvan · Pull Request #9265 · TheAlgorithms/Python · GitHub
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Enhance readability of N Queens#9265

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Oct 22, 2023
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Enhance readability of N Queens
#9265
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a1853d6

Enhance readability of N Queens


Hardvan Oct 1, 2023
631a3ce

Simplify is_safe code


Hardvan Oct 1, 2023
93937d4

[pre-commit.ci] auto fixes from pre-commit.com hooks


pre-commit-ci[bot] Oct 1, 2023
374faca

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tianyizheng02 Oct 22, 2023

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53 changes: 26 additions & 27 deletions
backtracking/n_queens.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -17,50 +17,49 @@ def is_safe(board: list[list[int]], row: int, column: int) -> bool:
 This function returns a boolean value True if it is safe to place a queen there
 considering the current state of the board.

 Parameters:
 board(2D matrix) : board
 row ,column : coordinates of the cell on a board
 Parameters:
 board(2D matrix): The chessboard
 row, column: Coordinates of the cell on the board

 Returns:
 Returns:
 Boolean Value

 """
 for i in range(len(board)):
 if board[row][i] == 1:
 return False
for i in range(len(board)):
 if board[i][column] == 1:
return False
 for i, j in zip(range(row, -1, -1), range(column, -1, -1)):
if board[i][j] == 1:
return False
for i, j in zip(range(row, -1, -1), range(column, len(board))):
if board[i][j] == 1:
 return False
return True

n = len(board) # Size of the board

# Check if there is any queen in the same row, column,
# left upper diagonal, and right upper diagonal
 return (
 all(board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, n)))
and all(
board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, -1, -1))
 )
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, n)))
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, -1, -1)))
)


def solve(board: list[list[int]], row: int) -> bool:
 """
It creates a state space tree and calls the safe function until it receives a
 False Boolean and terminates that branch and backtracks to the next
This function creates a state space tree and calls the safe function until it
receives a False Boolean and terminates that branch and backtracks to the next
 possible solution branch.
 """
 if row >= len(board):
 """
 If the row number exceeds N we have board with a successful combination
 If the row number exceeds N, we have a board with a successful combination
 and that combination is appended to the solution list and the board is printed.

 """
 solution.append(board)
 printboard(board)
 print()
 return True
 for i in range(len(board)):
 """
 For every row it iterates through each column to check if it is feasible to
 For every row, it iterates through each column to check if it is feasible to
 place a queen there.
 If all the combinations for that particular branch are successful the board is
 If all the combinations for that particular branch are successful, the board is
 reinitialized for the next possible combination.
 """
 if is_safe(board, row, i):
Expand All@@ -77,14 +76,14 @@ def printboard(board: list[list[int]]) -> None:
 for i in range(len(board)):
 for j in range(len(board)):
 if board[i][j] == 1:
 print("Q", end=" ")
 print("Q", end=" ") # Queen is present
 else:
 print(".", end=" ")
 print(".", end=" ") # Empty cell
 print()


# n=int(input("The no. of queens"))
# Number of queens (e.g., n=8 for an 8x8 board)
n = 8
board = [[0 for i in range(n)] for j in range(n)]
solve(board, 0)
print("The total no. of solutions are:", len(solution))
print("The total number of solutions are:", len(solution))

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
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color-scheme: dark light;
}
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Enhance readability of N Queens by Hardvan · Pull Request #9265 · TheAlgorithms/Python · GitHub
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Enhance readability of N Queens#9265

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 Merged

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Oct 22, 2023
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Enhance readability of N Queens
#9265
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a1853d6

Enhance readability of N Queens


Hardvan Oct 1, 2023
631a3ce

Simplify is_safe code


Hardvan Oct 1, 2023
93937d4

[pre-commit.ci] auto fixes from pre-commit.com hooks


pre-commit-ci[bot] Oct 1, 2023
374faca

Apply suggestions from code review


tianyizheng02 Oct 22, 2023

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53 changes: 26 additions & 27 deletions
backtracking/n_queens.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -17,50 +17,49 @@ def is_safe(board: list[list[int]], row: int, column: int) -> bool:
 This function returns a boolean value True if it is safe to place a queen there
 considering the current state of the board.

 Parameters:
 board(2D matrix) : board
 row ,column : coordinates of the cell on a board
 Parameters:
 board(2D matrix): The chessboard
 row, column: Coordinates of the cell on the board

 Returns:
 Returns:
 Boolean Value

 """
 for i in range(len(board)):
 if board[row][i] == 1:
 return False
for i in range(len(board)):
 if board[i][column] == 1:
return False
 for i, j in zip(range(row, -1, -1), range(column, -1, -1)):
if board[i][j] == 1:
return False
for i, j in zip(range(row, -1, -1), range(column, len(board))):
if board[i][j] == 1:
 return False
return True

n = len(board) # Size of the board

# Check if there is any queen in the same row, column,
# left upper diagonal, and right upper diagonal
 return (
 all(board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, n)))
and all(
board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, -1, -1))
 )
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, n)))
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, -1, -1)))
)


def solve(board: list[list[int]], row: int) -> bool:
 """
It creates a state space tree and calls the safe function until it receives a
 False Boolean and terminates that branch and backtracks to the next
This function creates a state space tree and calls the safe function until it
receives a False Boolean and terminates that branch and backtracks to the next
 possible solution branch.
 """
 if row >= len(board):
 """
 If the row number exceeds N we have board with a successful combination
 If the row number exceeds N, we have a board with a successful combination
 and that combination is appended to the solution list and the board is printed.

 """
 solution.append(board)
 printboard(board)
 print()
 return True
 for i in range(len(board)):
 """
 For every row it iterates through each column to check if it is feasible to
 For every row, it iterates through each column to check if it is feasible to
 place a queen there.
 If all the combinations for that particular branch are successful the board is
 If all the combinations for that particular branch are successful, the board is
 reinitialized for the next possible combination.
 """
 if is_safe(board, row, i):
Expand All@@ -77,14 +76,14 @@ def printboard(board: list[list[int]]) -> None:
 for i in range(len(board)):
 for j in range(len(board)):
 if board[i][j] == 1:
 print("Q", end=" ")
 print("Q", end=" ") # Queen is present
 else:
 print(".", end=" ")
 print(".", end=" ") # Empty cell
 print()


# n=int(input("The no. of queens"))
# Number of queens (e.g., n=8 for an 8x8 board)
n = 8
board = [[0 for i in range(n)] for j in range(n)]
solve(board, 0)
print("The total no. of solutions are:", len(solution))
print("The total number of solutions are:", len(solution))

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
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Enhance readability of N Queens by Hardvan · Pull Request #9265 · TheAlgorithms/Python · GitHub
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Enhance readability of N Queens#9265

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 Merged

tianyizheng02
merged 4 commits into

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Oct 22, 2023
 Merged


Enhance readability of N Queens
#9265
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a1853d6

Enhance readability of N Queens


Hardvan Oct 1, 2023
631a3ce

Simplify is_safe code


Hardvan Oct 1, 2023
93937d4

[pre-commit.ci] auto fixes from pre-commit.com hooks


pre-commit-ci[bot] Oct 1, 2023
374faca

Apply suggestions from code review


tianyizheng02 Oct 22, 2023

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53 changes: 26 additions & 27 deletions
backtracking/n_queens.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -17,50 +17,49 @@ def is_safe(board: list[list[int]], row: int, column: int) -> bool:
 This function returns a boolean value True if it is safe to place a queen there
 considering the current state of the board.

 Parameters:
 board(2D matrix) : board
 row ,column : coordinates of the cell on a board
 Parameters:
 board(2D matrix): The chessboard
 row, column: Coordinates of the cell on the board

 Returns:
 Returns:
 Boolean Value

 """
 for i in range(len(board)):
 if board[row][i] == 1:
 return False
for i in range(len(board)):
 if board[i][column] == 1:
return False
 for i, j in zip(range(row, -1, -1), range(column, -1, -1)):
if board[i][j] == 1:
return False
for i, j in zip(range(row, -1, -1), range(column, len(board))):
if board[i][j] == 1:
 return False
return True

n = len(board) # Size of the board

# Check if there is any queen in the same row, column,
# left upper diagonal, and right upper diagonal
 return (
 all(board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, n)))
and all(
board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, -1, -1))
 )
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, n)))
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, -1, -1)))
)


def solve(board: list[list[int]], row: int) -> bool:
 """
It creates a state space tree and calls the safe function until it receives a
 False Boolean and terminates that branch and backtracks to the next
This function creates a state space tree and calls the safe function until it
receives a False Boolean and terminates that branch and backtracks to the next
 possible solution branch.
 """
 if row >= len(board):
 """
 If the row number exceeds N we have board with a successful combination
 If the row number exceeds N, we have a board with a successful combination
 and that combination is appended to the solution list and the board is printed.

 """
 solution.append(board)
 printboard(board)
 print()
 return True
 for i in range(len(board)):
 """
 For every row it iterates through each column to check if it is feasible to
 For every row, it iterates through each column to check if it is feasible to
 place a queen there.
 If all the combinations for that particular branch are successful the board is
 If all the combinations for that particular branch are successful, the board is
 reinitialized for the next possible combination.
 """
 if is_safe(board, row, i):
Expand All@@ -77,14 +76,14 @@ def printboard(board: list[list[int]]) -> None:
 for i in range(len(board)):
 for j in range(len(board)):
 if board[i][j] == 1:
 print("Q", end=" ")
 print("Q", end=" ") # Queen is present
 else:
 print(".", end=" ")
 print(".", end=" ") # Empty cell
 print()


# n=int(input("The no. of queens"))
# Number of queens (e.g., n=8 for an 8x8 board)
n = 8
board = [[0 for i in range(n)] for j in range(n)]
solve(board, 0)
print("The total no. of solutions are:", len(solution))
print("The total number of solutions are:", len(solution))

, 'i');
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'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
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Enhance readability of N Queens by Hardvan · Pull Request #9265 · TheAlgorithms/Python · GitHub
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Enhance readability of N Queens#9265

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 Merged

tianyizheng02
merged 4 commits into

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Oct 22, 2023
 Merged


Enhance readability of N Queens
#9265
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a1853d6

Enhance readability of N Queens


Hardvan Oct 1, 2023
631a3ce

Simplify is_safe code


Hardvan Oct 1, 2023
93937d4

[pre-commit.ci] auto fixes from pre-commit.com hooks


pre-commit-ci[bot] Oct 1, 2023
374faca

Apply suggestions from code review


tianyizheng02 Oct 22, 2023

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53 changes: 26 additions & 27 deletions
backtracking/n_queens.py

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Original file line numberDiff line numberDiff line change
Expand Up@@ -17,50 +17,49 @@ def is_safe(board: list[list[int]], row: int, column: int) -> bool:
 This function returns a boolean value True if it is safe to place a queen there
 considering the current state of the board.

 Parameters:
 board(2D matrix) : board
 row ,column : coordinates of the cell on a board
 Parameters:
 board(2D matrix): The chessboard
 row, column: Coordinates of the cell on the board

 Returns:
 Returns:
 Boolean Value

 """
 for i in range(len(board)):
 if board[row][i] == 1:
 return False
for i in range(len(board)):
 if board[i][column] == 1:
return False
 for i, j in zip(range(row, -1, -1), range(column, -1, -1)):
if board[i][j] == 1:
return False
for i, j in zip(range(row, -1, -1), range(column, len(board))):
if board[i][j] == 1:
 return False
return True

n = len(board) # Size of the board

# Check if there is any queen in the same row, column,
# left upper diagonal, and right upper diagonal
 return (
 all(board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, n)))
and all(
board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, -1, -1))
 )
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, n)))
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, -1, -1)))
)


def solve(board: list[list[int]], row: int) -> bool:
 """
It creates a state space tree and calls the safe function until it receives a
 False Boolean and terminates that branch and backtracks to the next
This function creates a state space tree and calls the safe function until it
receives a False Boolean and terminates that branch and backtracks to the next
 possible solution branch.
 """
 if row >= len(board):
 """
 If the row number exceeds N we have board with a successful combination
 If the row number exceeds N, we have a board with a successful combination
 and that combination is appended to the solution list and the board is printed.

 """
 solution.append(board)
 printboard(board)
 print()
 return True
 for i in range(len(board)):
 """
 For every row it iterates through each column to check if it is feasible to
 For every row, it iterates through each column to check if it is feasible to
 place a queen there.
 If all the combinations for that particular branch are successful the board is
 If all the combinations for that particular branch are successful, the board is
 reinitialized for the next possible combination.
 """
 if is_safe(board, row, i):
Expand All@@ -77,14 +76,14 @@ def printboard(board: list[list[int]]) -> None:
 for i in range(len(board)):
 for j in range(len(board)):
 if board[i][j] == 1:
 print("Q", end=" ")
 print("Q", end=" ") # Queen is present
 else:
 print(".", end=" ")
 print(".", end=" ") # Empty cell
 print()


# n=int(input("The no. of queens"))
# Number of queens (e.g., n=8 for an 8x8 board)
n = 8
board = [[0 for i in range(n)] for j in range(n)]
solve(board, 0)
print("The total no. of solutions are:", len(solution))
print("The total number of solutions are:", len(solution))

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
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if (location.href !== lastUrl) {
lastUrl = location.href;
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observer.observe(document.body, { childList: true, subtree: true });
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})();
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try {
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Enhance readability of N Queens by Hardvan · Pull Request #9265 · TheAlgorithms/Python · GitHub
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#9265
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Enhance readability of N Queens


Hardvan Oct 1, 2023
631a3ce

Simplify is_safe code


Hardvan Oct 1, 2023
93937d4

[pre-commit.ci] auto fixes from pre-commit.com hooks


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374faca

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tianyizheng02 Oct 22, 2023

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53 changes: 26 additions & 27 deletions
backtracking/n_queens.py

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -17,50 +17,49 @@ def is_safe(board: list[list[int]], row: int, column: int) -> bool:
 This function returns a boolean value True if it is safe to place a queen there
 considering the current state of the board.

 Parameters:
 board(2D matrix) : board
 row ,column : coordinates of the cell on a board
 Parameters:
 board(2D matrix): The chessboard
 row, column: Coordinates of the cell on the board

 Returns:
 Returns:
 Boolean Value

 """
 for i in range(len(board)):
 if board[row][i] == 1:
 return False
for i in range(len(board)):
 if board[i][column] == 1:
return False
 for i, j in zip(range(row, -1, -1), range(column, -1, -1)):
if board[i][j] == 1:
return False
for i, j in zip(range(row, -1, -1), range(column, len(board))):
if board[i][j] == 1:
 return False
return True

n = len(board) # Size of the board

# Check if there is any queen in the same row, column,
# left upper diagonal, and right upper diagonal
 return (
 all(board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, n)))
and all(
board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, -1, -1))
 )
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, n)))
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, -1, -1)))
)


def solve(board: list[list[int]], row: int) -> bool:
 """
It creates a state space tree and calls the safe function until it receives a
 False Boolean and terminates that branch and backtracks to the next
This function creates a state space tree and calls the safe function until it
receives a False Boolean and terminates that branch and backtracks to the next
 possible solution branch.
 """
 if row >= len(board):
 """
 If the row number exceeds N we have board with a successful combination
 If the row number exceeds N, we have a board with a successful combination
 and that combination is appended to the solution list and the board is printed.

 """
 solution.append(board)
 printboard(board)
 print()
 return True
 for i in range(len(board)):
 """
 For every row it iterates through each column to check if it is feasible to
 For every row, it iterates through each column to check if it is feasible to
 place a queen there.
 If all the combinations for that particular branch are successful the board is
 If all the combinations for that particular branch are successful, the board is
 reinitialized for the next possible combination.
 """
 if is_safe(board, row, i):
Expand All@@ -77,14 +76,14 @@ def printboard(board: list[list[int]]) -> None:
 for i in range(len(board)):
 for j in range(len(board)):
 if board[i][j] == 1:
 print("Q", end=" ")
 print("Q", end=" ") # Queen is present
 else:
 print(".", end=" ")
 print(".", end=" ") # Empty cell
 print()


# n=int(input("The no. of queens"))
# Number of queens (e.g., n=8 for an 8x8 board)
n = 8
board = [[0 for i in range(n)] for j in range(n)]
solve(board, 0)
print("The total no. of solutions are:", len(solution))
print("The total number of solutions are:", len(solution))

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
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}
});
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observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Enhance readability of N Queens by Hardvan · Pull Request #9265 · TheAlgorithms/Python · GitHub
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Enhance readability of N Queens#9265

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 Merged

tianyizheng02
merged 4 commits into

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Oct 22, 2023
 Merged


Enhance readability of N Queens
#9265
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a1853d6

Enhance readability of N Queens


Hardvan Oct 1, 2023
631a3ce

Simplify is_safe code


Hardvan Oct 1, 2023
93937d4

[pre-commit.ci] auto fixes from pre-commit.com hooks


pre-commit-ci[bot] Oct 1, 2023
374faca

Apply suggestions from code review


tianyizheng02 Oct 22, 2023

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53 changes: 26 additions & 27 deletions
backtracking/n_queens.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -17,50 +17,49 @@ def is_safe(board: list[list[int]], row: int, column: int) -> bool:
 This function returns a boolean value True if it is safe to place a queen there
 considering the current state of the board.

 Parameters:
 board(2D matrix) : board
 row ,column : coordinates of the cell on a board
 Parameters:
 board(2D matrix): The chessboard
 row, column: Coordinates of the cell on the board

 Returns:
 Returns:
 Boolean Value

 """
 for i in range(len(board)):
 if board[row][i] == 1:
 return False
for i in range(len(board)):
 if board[i][column] == 1:
return False
 for i, j in zip(range(row, -1, -1), range(column, -1, -1)):
if board[i][j] == 1:
return False
for i, j in zip(range(row, -1, -1), range(column, len(board))):
if board[i][j] == 1:
 return False
return True

n = len(board) # Size of the board

# Check if there is any queen in the same row, column,
# left upper diagonal, and right upper diagonal
 return (
 all(board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, n)))
and all(
board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, -1, -1))
 )
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, n)))
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, -1, -1)))
)


def solve(board: list[list[int]], row: int) -> bool:
 """
It creates a state space tree and calls the safe function until it receives a
 False Boolean and terminates that branch and backtracks to the next
This function creates a state space tree and calls the safe function until it
receives a False Boolean and terminates that branch and backtracks to the next
 possible solution branch.
 """
 if row >= len(board):
 """
 If the row number exceeds N we have board with a successful combination
 If the row number exceeds N, we have a board with a successful combination
 and that combination is appended to the solution list and the board is printed.

 """
 solution.append(board)
 printboard(board)
 print()
 return True
 for i in range(len(board)):
 """
 For every row it iterates through each column to check if it is feasible to
 For every row, it iterates through each column to check if it is feasible to
 place a queen there.
 If all the combinations for that particular branch are successful the board is
 If all the combinations for that particular branch are successful, the board is
 reinitialized for the next possible combination.
 """
 if is_safe(board, row, i):
Expand All@@ -77,14 +76,14 @@ def printboard(board: list[list[int]]) -> None:
 for i in range(len(board)):
 for j in range(len(board)):
 if board[i][j] == 1:
 print("Q", end=" ")
 print("Q", end=" ") # Queen is present
 else:
 print(".", end=" ")
 print(".", end=" ") # Empty cell
 print()


# n=int(input("The no. of queens"))
# Number of queens (e.g., n=8 for an 8x8 board)
n = 8
board = [[0 for i in range(n)] for j in range(n)]
solve(board, 0)
print("The total no. of solutions are:", len(solution))
print("The total number of solutions are:", len(solution))

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
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if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
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Enhance readability of N Queens by Hardvan · Pull Request #9265 · TheAlgorithms/Python · GitHub
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Enhance readability of N Queens#9265

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 Merged

tianyizheng02
merged 4 commits into

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Oct 22, 2023
 Merged


Enhance readability of N Queens
#9265
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Commits

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4 commits


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a1853d6

Enhance readability of N Queens


Hardvan Oct 1, 2023
631a3ce

Simplify is_safe code


Hardvan Oct 1, 2023
93937d4

[pre-commit.ci] auto fixes from pre-commit.com hooks


pre-commit-ci[bot] Oct 1, 2023
374faca

Apply suggestions from code review


tianyizheng02 Oct 22, 2023

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53 changes: 26 additions & 27 deletions
backtracking/n_queens.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -17,50 +17,49 @@ def is_safe(board: list[list[int]], row: int, column: int) -> bool:
 This function returns a boolean value True if it is safe to place a queen there
 considering the current state of the board.

 Parameters:
 board(2D matrix) : board
 row ,column : coordinates of the cell on a board
 Parameters:
 board(2D matrix): The chessboard
 row, column: Coordinates of the cell on the board

 Returns:
 Returns:
 Boolean Value

 """
 for i in range(len(board)):
 if board[row][i] == 1:
 return False
for i in range(len(board)):
 if board[i][column] == 1:
return False
 for i, j in zip(range(row, -1, -1), range(column, -1, -1)):
if board[i][j] == 1:
return False
for i, j in zip(range(row, -1, -1), range(column, len(board))):
if board[i][j] == 1:
 return False
return True

n = len(board) # Size of the board

# Check if there is any queen in the same row, column,
# left upper diagonal, and right upper diagonal
 return (
 all(board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, n)))
and all(
board[i][j] != 1 for i, j in zip(range(row, -1, -1), range(column, -1, -1))
 )
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, n)))
and all(board[i][j] != 1 for i, j in zip(range(row, n), range(column, -1, -1)))
)


def solve(board: list[list[int]], row: int) -> bool:
 """
It creates a state space tree and calls the safe function until it receives a
 False Boolean and terminates that branch and backtracks to the next
This function creates a state space tree and calls the safe function until it
receives a False Boolean and terminates that branch and backtracks to the next
 possible solution branch.
 """
 if row >= len(board):
 """
 If the row number exceeds N we have board with a successful combination
 If the row number exceeds N, we have a board with a successful combination
 and that combination is appended to the solution list and the board is printed.

 """
 solution.append(board)
 printboard(board)
 print()
 return True
 for i in range(len(board)):
 """
 For every row it iterates through each column to check if it is feasible to
 For every row, it iterates through each column to check if it is feasible to
 place a queen there.
 If all the combinations for that particular branch are successful the board is
 If all the combinations for that particular branch are successful, the board is
 reinitialized for the next possible combination.
 """
 if is_safe(board, row, i):
Expand All@@ -77,14 +76,14 @@ def printboard(board: list[list[int]]) -> None:
 for i in range(len(board)):
 for j in range(len(board)):
 if board[i][j] == 1:
 print("Q", end=" ")
 print("Q", end=" ") # Queen is present
 else:
 print(".", end=" ")
 print(".", end=" ") # Empty cell
 print()


# n=int(input("The no. of queens"))
# Number of queens (e.g., n=8 for an 8x8 board)
n = 8
board = [[0 for i in range(n)] for j in range(n)]
solve(board, 0)
print("The total no. of solutions are:", len(solution))
print("The total number of solutions are:", len(solution))