Create cousins-in-binary-tree.py

Author: kamyu104

Python/cousins-in-binary-tree.py

@@ -0,0 +1,43 @@
+# Time:  O(n)
+# Space: O(h)
+
+# Definition for a binary tree node.
+class TreeNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+
+class Solution(object):
+    def isCousins(self, root, x, y):
+        """
+        :type root: TreeNode
+        :type x: int
+        :type y: int
+        :rtype: bool
+        """
+        def dfs(root, x, depth, parent):
+            if not root:
+                return False
+            if root.val == x:
+                return True
+            depth[0] += 1
+            prev_parent, parent[0] = parent[0], root
+            if dfs(root.left, x, depth, parent):
+                return True
+            parent[0] = root
+            if dfs(root.right, x, depth, parent):
+                return True
+            parent[0] = prev_parent
+            depth[0] -= 1
+            return False
+        
+        depth_x, depth_y = [0], [0]
+        parent_x, parent_y = [None], [None]
+        return dfs(root, x, depth_x, parent_x) and \
+               dfs(root, y, depth_y, parent_y) and \
+               depth_x[0] == depth_y[0] and \
+               parent_x[0] != parent_y[0]
+                
+