Create 226-invert_binary_tree.py

Author: stevestar888

Diff for: 226-invert_binary_tree.py

@@ -0,0 +1,62 @@
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution(object):
+    """
+    Recursive 
+    
+    Stats: O(n) time, O(1) space
+        Runtime: 32 ms, faster than 7.14% of Python online submissions for Invert Binary Tree.
+        Memory Usage: 12.7 MB, less than 50.80% of Python online submissions for Invert Binary Tree.
+    """
+    def invertTree(self, root):
+        """
+        :type root: TreeNode
+        :rtype: TreeNode
+        """
+        ### base case
+        if root == None:
+            return
+        
+        #swap the left & right children with each other
+        root.left, root.right = root.right, root.left
+
+        #now swap for other future generations
+        self.invertTree(root.left)
+        self.invertTree(root.right)
+        
+        return root
+    
+    """
+    Iterative
+    
+    Stats: O(n) time, O(1) space
+        Runtime: 20 ms, faster than 61.22% of Python online submissions for Invert Binary Tree.
+        Memory Usage: 12.7 MB, less than 54.22% of Python online submissions for Invert Binary Tree.
+    """
+    def invertTree(self, root):
+        """
+        :type root: TreeNode
+        :rtype: TreeNode
+        """
+        if not root:
+            return None
+        
+        stack = deque()
+        stack.append(root)
+        
+        while stack:
+            node = stack.popleft()
+            
+            #swap the left & right children with each other
+            node.left, node.right = node.right, node.left
+            
+            if node.left:
+                stack.append(node.left)
+            if node.right:
+                stack.append(node.right)
+                
+        return root