JZ28 对称的二叉树

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};
*/
class Solution {
public:
    bool match (TreeNode * t1, TreeNode *t2) {
           if (!t1 && !t2) return 1;
            if (!t1 || !t2) return 0;
          return t1->val == t2->val && 
                match(t1->left, t2->right) &&
                  match(t1->right, t2->left);
    }
    bool isSymmetrical(TreeNode* pRoot) {
       return match(pRoot, pRoot);
    }

};

注意子问题作为终止条件