[Binary Tree] Different views of binary tree added (#6965)

* Different views of binary tree added

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* Update data_structures/binary_tree/diff_views_of_binary_tree.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update data_structures/binary_tree/diff_views_of_binary_tree.py

Co-authored-by: Christian Clauss <cclauss@me.com>

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* Update diff_views_of_binary_tree.py

* Update diff_views_of_binary_tree.py

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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()