LeetCode 653. Two Sum IV – Input is a BST
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
/**
* 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:
void dfs(TreeNode* root){
if(root==NULL) return;
nums.push_back(root->val);
checked[root->val]++;
dfs(root->left);
dfs(root->right);
}
bool findTarget(TreeNode* root, int k) {
dfs(root);
for(int i=0;i<nums.size();i++)
if(k-nums[i]!=nums[i]&&checked[k-nums[i]]>=1)
return true;
else if(k-nums[i]==nums[i]&&checked[nums[i]]>=2)
return true;
return false;
}
private:
vector<int> nums;
map<int,int> checked;
};