LeetCode_SameTree

100. Same Tree

Total Accepted: 102505 Total Submissions: 241539 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.

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如题，判断两个二叉树是否是相同的：

思路是：判断其节点是否相同，然后再判断其子节点。

public class Solution {    public boolean isSameTree(TreeNode p, TreeNode q) {        if(p==q){            if(isSameTree(p.left,q.left)&&isSameTree(p.right,q.right)){                return true;                            }                    }        return false;    }}

 然而这种做法是不对的，因为节点p和q的引用是不同的，所以不能这样判断，造成的结果就是本来是相同的树，也会识别错误。  改正后

还是会报错：

 if(p.val==q.val){

Line 14: java.lang.NullPointerException

好吧，空指针错误，于是，

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){            if(isSameTree(p.left,q.left)&&isSameTree(p.right,q.right)){                return true;                            }        }        return false;    }}

世界安静了！