leetcode 572 另一棵樹的子樹

題目地址：https://leetcode-cn.com/problems/subtree-of-another-tree/

DFS暴力求解：

/**
 * 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 check(TreeNode*s, TreeNode* t){
        if(!s && !t){
            return true;
        }
        if((!s&&t) || (s&&!t) || (s->val != t->val)){
            return false;
        }
        return (check(s->left, t->left) && check(s->right, t->right));

    }
    bool dfs(TreeNode* s, TreeNode* t){
        if(!s){
            return false;
        }
        return (check(s,t) || dfs(s->left, t) || dfs(s->right, t));
    }
    bool isSubtree(TreeNode* s, TreeNode* t) {
        return dfs(s,t);
    }
};

KMP求解：