LeetCode (65):Same tree

Total Accepted: 83663 Total Submissions: 200541 Difficulty: Easy

 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.

 

首先想到的是递归法，判断过程为依次遍历每一个点如果有：

1. 如果都为null或是都不为null且值相等返回true
2. 一个为Null另一个不为Null返回false
3. 两个都不为null但值不相等返回false

代码如下：

class TreeNode{
       int val;
            TreeNode left;
           TreeNode right;
            TreeNode(int x) { val = x; }
}
public class Solution {
     public static boolean isSameTree(TreeNode p, TreeNode q) {
         if(p==null&&q==null)     return true;  //同时到达叶子节点
         else  if(p==null||q==null) return false;   //不同时到达叶子则不相同
         if(p.val!=q.val) return false;  //节点值不同则不相同
         else return isSameTree(p.left, q.left)&&isSameTree(p.right, q.right); //递归
                                                                    
     }
           //测试
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        TreeNode t1=new TreeNode(1);
        TreeNode nodeB=new TreeNode(2);
        t1.left=nodeB;
        
        TreeNode t2=new TreeNode(1);
        TreeNode nodeB1=new TreeNode(2);
        t2.left=nodeB1;        
        System.out.println(isSameTree(t1,t2));
    }

}