LeetCode

Same Tree

2013.12.31 22:56

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.

Solution:

　　Check the root, the left subtree and the right subtree, recursively. That's the answer.

　　Time complexity is O(min(m, n)), where m and n are the numbers of nodes in both trees.

　　Space complexity is O(1).

Accepted code:

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isSameTree(TreeNode *p, TreeNode *q) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(p == nullptr || q == nullptr){
            return p == q;
        }else{
            if(p->val == q->val){
                return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
            }else{
                return false;
            }
        }
    }
};