Python/data_structures/binary_tree/diff_views_of_binary_tree.py at master · twilight-debugger/Python · GitHub

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r"""
Problem: Given root of a binary tree, return the:
1. binary-tree-right-side-view
2. binary-tree-left-side-view
3. binary-tree-top-side-view
4. binary-tree-bottom-side-view
"""

from __future__ importannotations

fromcollectionsimportdefaultdict
fromdataclassesimportdataclass


@dataclass
classTreeNode:
val: int
left: TreeNode|None=None
right: TreeNode|None=None


defmake_tree() ->TreeNode:
"""
 >>> make_tree().val
 3
 """
returnTreeNode(3, TreeNode(9), TreeNode(20, TreeNode(15), TreeNode(7)))


defbinary_tree_right_side_view(root: TreeNode) ->list[int]:
r"""
 Function returns the right side view of binary tree.

 3 <- 3
 / \
 9 20 <- 20
 / \
 15 7 <- 7

 >>> binary_tree_right_side_view(make_tree())
 [3, 20, 7]
 >>> binary_tree_right_side_view(None)
 []
 """

defdepth_first_search(
root: TreeNode|None, depth: int, right_view: list[int]
 ) ->None:
"""
 A depth first search preorder traversal to append the values at
 right side of tree.
 """
ifnotroot:
return

ifdepth==len(right_view):
right_view.append(root.val)

depth_first_search(root.right, depth+1, right_view)
depth_first_search(root.left, depth+1, right_view)

right_view: list= []
ifnotroot:
returnright_view

depth_first_search(root, 0, right_view)
returnright_view


defbinary_tree_left_side_view(root: TreeNode) ->list[int]:
r"""
 Function returns the left side view of binary tree.

 3 -> 3
 / \
 9 -> 9 20
 / \
 15 -> 15 7

 >>> binary_tree_left_side_view(make_tree())
 [3, 9, 15]
 >>> binary_tree_left_side_view(None)
 []
 """

defdepth_first_search(
root: TreeNode|None, depth: int, left_view: list[int]
 ) ->None:
"""
 A depth first search preorder traversal to append the values
 at left side of tree.
 """
ifnotroot:
return

ifdepth==len(left_view):
left_view.append(root.val)

depth_first_search(root.left, depth+1, left_view)
depth_first_search(root.right, depth+1, left_view)

left_view: list= []
ifnotroot:
returnleft_view

depth_first_search(root, 0, left_view)
returnleft_view


defbinary_tree_top_side_view(root: TreeNode) ->list[int]:
r"""
 Function returns the top side view of binary tree.

 9 3 20 7
 ⬇ ⬇ ⬇ ⬇

 3
 / \
 9 20
 / \
 15 7

 >>> binary_tree_top_side_view(make_tree())
 [9, 3, 20, 7]
 >>> binary_tree_top_side_view(None)
 []
 """

defbreadth_first_search(root: TreeNode, top_view: list[int]) ->None:
"""
 A breadth first search traversal with defaultdict ds to append
 the values of tree from top view
 """
queue= [(root, 0)]
lookup=defaultdict(list)

whilequeue:
first=queue.pop(0)
node, hd=first

lookup[hd].append(node.val)

ifnode.left:
queue.append((node.left, hd-1))
ifnode.right:
queue.append((node.right, hd+1))

forpairinsorted(lookup.items(), key=lambdaeach: each[0]):
top_view.append(pair[1][0])

top_view: list= []
ifnotroot:
returntop_view

breadth_first_search(root, top_view)
returntop_view


defbinary_tree_bottom_side_view(root: TreeNode) ->list[int]:
r"""
 Function returns the bottom side view of binary tree

 3
 / \
 9 20
 / \
 15 7
 ↑ ↑ ↑ ↑
 9 15 20 7

 >>> binary_tree_bottom_side_view(make_tree())
 [9, 15, 20, 7]
 >>> binary_tree_bottom_side_view(None)
 []
 """
fromcollectionsimportdefaultdict

defbreadth_first_search(root: TreeNode, bottom_view: list[int]) ->None:
"""
 A breadth first search traversal with defaultdict ds to append
 the values of tree from bottom view
 """
queue= [(root, 0)]
lookup=defaultdict(list)

whilequeue:
first=queue.pop(0)
node, hd=first
lookup[hd].append(node.val)

ifnode.left:
queue.append((node.left, hd-1))
ifnode.right:
queue.append((node.right, hd+1))

forpairinsorted(lookup.items(), key=lambdaeach: each[0]):
bottom_view.append(pair[1][-1])

bottom_view: list= []
ifnotroot:
returnbottom_view

breadth_first_search(root, bottom_view)
returnbottom_view


if__name__=="__main__":
importdoctest

doctest.testmod()