leedcode_100. Same Tree

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.

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題目簡單，遞歸的一個調用遍歷一遍樹就好了。qp同時遍歷，不同就返回。

代碼：

/**
 * 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 {
public:
    bool isSameTree(TreeNode* p, TreeNode* q) {
        if(p == NULL && q == NULL){
            return 1;
        }
        if(p == NULL || q == NULL){
            return 0;
        }
        if(p->val == q->val){
            return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
        }
        if(p->val != q->val){
            return 0;
        }
        return 1;
    }
};