[Second]Same Tree

树的问题，优先考虑递归。

/**
 * 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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(!p&&!q)
            return true;
        if(!p||!q||p->val!=q->val)
            return false;
        if(isSameTree(p->left,q->left)&&isSameTree(p->right,q->right))
            return true;
        else return false;
        
    }
};