沒錯我就是伍聲2009的粉絲，從今天起，模仿《從零單排》系列，菜雞單刷LeetCode！

題目：

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.

解答：

驗證兩棵樹是否相等。使用遞迴的思想，如果樹節點的val相等，則去各自計運算元樹是否是相等的樹。

注意遞迴終點：輸入的兩棵樹全部都是空樹

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

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