leetcode-- 100. Same Tree

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1、问题描述

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.

2、边界条件:无

3、思路:递归,两颗数is same的条件是val相等,子树也是same。但是判断val的前提条件是有val,即不为null。

base case:两颗数都为空;一颗为空,一颗不为空。

4、代码实现

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean isSameTree(TreeNode p, TreeNode q) {
        if (p == null && q == null) {//base case是两个节点都为空
            return true;
        }
        if (p == null || q == null) {
            return false;
        }
        return p.val == q.val
               && isSameTree(p.left, q.left)
               && isSameTree(p.right, q.right);
    }
}

 

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