LeetCode 653. 两数之和 IV - 输入 BST
原题链接
简单
/**
* 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:
unordered_set<int> record;
bool findTarget(TreeNode* root, int k) {
return dfs(root, k);
}
bool dfs(TreeNode* root, int k) {
if(!root) return false;
if(dfs(root->left, k)) return true;
int x = root->val;
if(record.count(k - x)) return true;
record.insert(x);
return dfs(root->right, k);
}
};