same-tree.py

# Time:  O(n)
# Space: O(h), h is height of binary tree
#
# Given two binary trees, write a function to check if they are equal or not.
# 
# Two binary trees are considered equal if they are structurally identical and the nodes have the same value.
#

# Definition for a  binary tree node
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution:
    # @param p, a tree node
    # @param q, a tree node
    # @return a boolean
    def isSameTree(self, p, q):
        if p is None and q is None:
            return True
        
        if p is not None and q is not None:
            return p.val == q.val and self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)
        
        return False
    
if __name__ == "__main__":
    root1, root1.left, root1.right = TreeNode(1), TreeNode(2), TreeNode(3)
    root2, root2.left, root2.right = TreeNode(1), TreeNode(2), TreeNode(3)
    print Solution().isSameTree(root1, root2)