100. Same 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.

递归求解比较简单，遍历过程中，如果p和q都是null或者p和q的val相等，返回true，如果p和q只有一方是null或者p和q的val不相等，返回false，代码如下：

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