题意ref{:target=”_blank”}
注意两个函数的区别
isSubtree用来遍历整棵树;
isSame用来判断2棵树相等
C++ 代码
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
bool isSubtree(TreeNode* root, TreeNode* subRoot) {
// isSubtree 用来遍历这棵树的每一个节点
if(!root)return false;
if(isSame(root, subRoot))return true;
return isSubtree(root->left, subRoot) || isSubtree(root->right, subRoot);
}
// isSame 判断两棵树r和s是否相同
bool isSame(TreeNode* r, TreeNode* s) {
// 同时为空
if(!r && !s)return true;
// 有一个为空
if(!r&&s || r&&!s || r->val!=s->val)return false;
return isSame(r->left, s->left) && isSame(r->right, s->right);
}
};
补充题目
树的子结构
剑指offer连接{:target=”_blank”}
/**
* 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 isSubStructure(TreeNode* A, TreeNode* B) {
if(!B)return false;
if(!A)return false;
if(isSub(A, B)) return true;
return isSubStructure(A->left, B) || isSubStructure(A->right, B);
}
bool isSub(TreeNode* r, TreeNode* s) {
// 注意这里和 subtree 的区别
// s为空就说明匹配了,不管r
if(!s)return true;
if(!r&&s || r->val!=s->val)return false;
return isSub(r->left, s->left) && isSub(r->right, s->right);
}
};