Algorithm-and-Data-Structure/AlgorithmCode/Sudoku.java at master · lemidia/Algorithm-and-Data-Structure · GitHub

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importjava.io.BufferedReader;
importjava.io.IOException;
importjava.io.InputStreamReader;
importjava.util.StringTokenizer;

publicclassSudoku {

privatestaticintsudokuMatrix[][];
privatestaticbooleanskip[][];

publicstaticbooleanisValidPlacement(introw, intcol) {
// Row inspection
intvalue = sudokuMatrix[row][col];
for (inti = 0; i < 9; i++) {
if (i == col)
continue;
elseif (sudokuMatrix[row][i] == value) {
returnfalse;
 }
 }

// Column inspection
for (inti = 0; i < 9; i++) {
if (i == row)
continue;
elseif (sudokuMatrix[i][col] == value) {
returnfalse;
 }
 }

// 3x3 Small Grid inspection
intbaseRow = (row/3)*3;
intbaseCol = (col/3)*3;
for (inti = baseRow; i < baseRow+3 ; i++) {
for (intj = baseCol; j < baseCol+3 ; j++) {
if (i == row && j == col)
continue;
elseif (sudokuMatrix[i][j] == value)
returnfalse;
 }
 }
returntrue;
 }

publicstaticbooleansolve(introw, intcol) {
// Final Goal Case
if (row == 9)
returntrue;

if (skip[row][col]) {
if (col+1 != 9){
if (solve(row, col+1))
returntrue;
 }
else {
if (solve(row+1, 0))
returntrue;
 }
 } else {
for (inti = 1; i < 10; i++) {
sudokuMatrix[row][col] = i;
if (isValidPlacement(row, col)) {
if (col+1 != 9){
if (solve(row, col+1))
returntrue;
 }
else {
if (solve(row+1, 0))
returntrue;
 }
 }
 }
sudokuMatrix[row][col] = 0;
 }

returnfalse;
 }

publicstaticvoidmain(String[] args)throwsIOException {
BufferedReaderbr = newBufferedReader(newInputStreamReader(System.in));

sudokuMatrix = newint[9][9];
skip = newboolean[9][9];

// Sample Input:
// 3 0 6 5 0 8 4 0 0
// 5 2 0 0 0 0 0 0 0
// 0 8 7 0 0 0 0 3 1
// 0 0 3 0 1 0 0 8 0
// 9 0 0 8 6 3 0 0 5
// 0 5 0 0 9 0 6 0 0
// 1 3 0 0 0 0 2 5 0
// 0 0 0 0 0 0 0 7 4
// 0 0 5 2 0 6 3 0 0

for (inti = 0; i < 9; i++) {
StringTokenizerst = newStringTokenizer(br.readLine(), " ");
for (intj = 0; j < 9; j++) {
sudokuMatrix[i][j] = Integer.parseInt(st.nextToken());
if (sudokuMatrix[i][j] > 0)
skip[i][j] = true;
 }
 }

// Sample Output:
// The Sudoku have been solved!
//
// 3 1 6 5 7 8 4 9 2
// 5 2 9 1 3 4 7 6 8
// 4 8 7 6 2 9 5 3 1
// 2 6 3 4 1 5 9 8 7
// 9 7 4 8 6 3 1 2 5
// 8 5 1 7 9 2 6 4 3
// 1 3 8 9 4 7 2 5 6
// 6 9 2 3 5 1 8 7 4
// 7 4 5 2 8 6 3 1 9

if (solve(0, 0)){
System.out.println("The Sudoku have been solved!" + "\n");
for (inti = 0; i < 9; i++) {
for (intj = 0; j < 9; j++) {
System.out.print(sudokuMatrix[i][j] + " ");
 }
System.out.println();
 }
 }else {
System.out.println("The Sudoku could not be solved!");
 }
 }
}