【Leetcode】100. Same Tree（检测两棵二叉树是否相同）

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Given two binary trees, write a function to check if they are the same or not.

Two binary trees are considered the same if they are structurally identical and the nodes have the same value.

Example 1:

Input:     1         1
          / \       / \
         2   3     2   3

        [1,2,3],   [1,2,3]

Output: true

Example 2:

Input:     1         1
          /           \
         2             2

        [1,2],     [1,null,2]

Output: false

Example 3:

Input:     1         1
          / \       / \
         2   1     1   2

        [1,2,1],   [1,1,2]

Output: false

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
private:
    bool valid(TreeNode* p, TreeNode* q){
        
        if(p==NULL&&q==NULL){
            return true;
        }else if(p!=NULL&&q!=NULL){
            if(p->val!=q->val){
                return false;
            }else{
                return (valid(p->left, q->left)&&valid(p->right, q->right));
            }
        }else{
            return false;
        }    
    }
public:
    bool isSameTree(TreeNode* p, TreeNode* q) {
        if(p!=NULL&&q!=NULL){
            return valid(p,q);
        }
        else if (p==NULL&&q==NULL){
            return true;
        }
        else{
            return false;
        }
    }
};