Title
Given a Binary Search Tree and a target number, return true if there exist two elements in the BST such that their sum is equal to the given target.
Example 1:
Input:
5
/ \
3 6
/ \ \
2 4 7
Target = 9
Output: True
Example 2:
Input:
5
/ \
3 6
/ \ \
2 4 7
Target = 28
Output: False
查看树的节点中是否有两个节点的和为某一个值
Solution
//cpp:
/**
* 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 find(TreeNode* t,unordered_set<int> &set1,int k){
if(!t)
return false;
if(set1.find(k-t->val)!=set1.end()){
return true;
}
set1.insert(t->val);
return find(t->left,set1,k)||find(t->right,set1,k);
}
bool findTarget(TreeNode* root, int k) {
unordered_set<int> set1;
return find(root,set1,k);
}
};