572. Subtree of Another Tree

题目描述【Leetcode】

Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node’s descendants. The tree s could also be considered as a subtree of itself.

Example 1:
Given tree s:
…….3
….. / \
…. 4 5
…./ \
…1 2
Given tree t:
…..4
…./ \
…1 2
Return true, because t has the same structure and node values with a subtree of s.

Example 2:
Given tree s:
….3
…/ \
..4 5
./ \
1 2
.. /
..0
Given tree t:
…. 4
…./ \
…1 2
Return false.

判断某个树是否为另一个的子树

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */bool f(TreeNode* s, TreeNode* t){        if (!s) return t == NULL;        if (!t) return false;        return s->val == t->val && f(s->left,t->left) && f(s->right,t->right);}class Solution {public:    bool isSubtree(TreeNode* s, TreeNode* t) {        if(!s)return t == NULL;        if(!t) return false;        return isSubtree(s->left,t) || isSubtree(s->right,t) || f(s,t);    }};