Merge Two Binary Trees

Author: anantkaushik

617-merge-two-binary-trees.py

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+"""
+Problem Link: https://leetcode.com/problems/merge-two-binary-trees/
+
+Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the 
+others are not.
+You need to merge them into a new binary tree. The merge rule is that if two nodes overlap, then sum node values up as the new value of the 
+merged node. Otherwise, the NOT null node will be used as the node of new tree.
+
+Example 1:
+Input: 
+	Tree 1                     Tree 2                  
+          1                         2                             
+         / \                       / \                            
+        3   2                     1   3                        
+       /                           \   \                      
+      5                             4   7                  
+Output: 
+Merged tree:
+	     3
+	    / \
+	   4   5
+	  / \   \ 
+	 5   4   7
+
+Note: The merging process must start from the root nodes of both trees.
+"""
+# 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 mergeTrees(self, t1, t2):
+        """
+        :type t1: TreeNode
+        :type t2: TreeNode
+        :rtype: TreeNode
+        """
+        if t1 is None:
+            return t2
+        if t2 is None:
+            return t1
+        t1.val += t2.val
+        t1.left = self.mergeTrees(t1.left,t2.left)
+        t1.right = self.mergeTrees(t1.right,t2.right)
+        return t1