lintcode/leetcode由易至难第11题：Same Tree

Problem:

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.

Code:

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

Code2:

public boolean isSameTree(TreeNode p, TreeNode q) {    if(p == null && q == null) return true;    if(p == null || q == null) return false;  //第一个if已经排除掉左右都为true了    if(p.val == q.val)        return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);    return false;  //此处可以省略else}