From 3448ae5cec868d4a03349cb952765e9abff41243 Mon Sep 17 00:00:00 2001 From: Shubham Kondekar <40213815+kondekarshubham123@users.noreply.github.com> Date: Tue, 18 Oct 2022 02:00:01 +0530 Subject: [PATCH] [Binary Tree] Different views of binary tree added (#6965) * Different views of binary tree added * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * mypy errors resolved * doc test for remaining functions * Flake8 comments resolved * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * Example moved in if block * doctest cases added * Cases from if block removed * Update data_structures/binary_tree/diff_views_of_binary_tree.py Co-authored-by: Christian Clauss * Update data_structures/binary_tree/diff_views_of_binary_tree.py Co-authored-by: Christian Clauss * PR Comments resolved * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * flake8 warning resolved * Changes revered * flake8 issue resolved * Put the diagrams just above the doctests * Update diff_views_of_binary_tree.py * Update diff_views_of_binary_tree.py * I love mypy * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Christian Clauss --- .../binary_tree/diff_views_of_binary_tree.py | 210 ++++++++++++++++++ 1 file changed, 210 insertions(+) create mode 100644 data_structures/binary_tree/diff_views_of_binary_tree.py diff --git a/data_structures/binary_tree/diff_views_of_binary_tree.py b/data_structures/binary_tree/diff_views_of_binary_tree.py new file mode 100644 index 000000000..3198d8065 --- /dev/null +++ b/data_structures/binary_tree/diff_views_of_binary_tree.py @@ -0,0 +1,210 @@ +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__ import annotations + +from collections import defaultdict +from dataclasses import dataclass + + +@dataclass +class TreeNode: + val: int + left: TreeNode | None = None + right: TreeNode | None = None + + +def make_tree() -> TreeNode: + """ + >>> make_tree().val + 3 + """ + return TreeNode(3, TreeNode(9), TreeNode(20, TreeNode(15), TreeNode(7))) + + +def binary_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) + [] + """ + + def depth_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. + """ + if not root: + return + + if depth == 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 = [] + if not root: + return right_view + + depth_first_search(root, 0, right_view) + return right_view + + +def binary_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) + [] + """ + + def depth_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. + """ + if not root: + return + + if depth == 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 = [] + if not root: + return left_view + + depth_first_search(root, 0, left_view) + return left_view + + +def binary_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) + [] + """ + + def breadth_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) + + while queue: + first = queue.pop(0) + node, hd = first + + lookup[hd].append(node.val) + + if node.left: + queue.append((node.left, hd - 1)) + if node.right: + queue.append((node.right, hd + 1)) + + for pair in sorted(lookup.items(), key=lambda each: each[0]): + top_view.append(pair[1][0]) + + top_view: list = [] + if not root: + return top_view + + breadth_first_search(root, top_view) + return top_view + + +def binary_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) + [] + """ + from collections import defaultdict + + def breadth_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) + + while queue: + first = queue.pop(0) + node, hd = first + lookup[hd].append(node.val) + + if node.left: + queue.append((node.left, hd - 1)) + if node.right: + queue.append((node.right, hd + 1)) + + for pair in sorted(lookup.items(), key=lambda each: each[0]): + bottom_view.append(pair[1][-1]) + + bottom_view: list = [] + if not root: + return bottom_view + + breadth_first_search(root, bottom_view) + return bottom_view + + +if __name__ == "__main__": + import doctest + + doctest.testmod()