算法：Same Tree

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.

/**
 * 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 isNodeEqual(TreeNode* n1, TreeNode* n2)
    {
        if(n1==NULL && n2==NULL)
            return true;
        if(n1==NULL || n2==NULL)
            return false;
        
        return (n1->val==n2->val) && isNodeEqual(n1->left, n2->left) && isNodeEqual(n1->right, n2->right);
    }
    
public:
    bool isSameTree(TreeNode* p, TreeNode* q) {
        return isNodeEqual(p, q);
    }
};