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.

判断两棵二叉树是否相同。

思路是依次比较两棵树上左子树的各个节点的值是否相同，然后再比较右子树。

/** * 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 || q == null && p != null || p.val != q.val) {return false;}return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);    }    }