LeetCode 272. Closest Binary Search Tree Value II

#include 
#include 
using namespace std;

/*
  Given a non-empty binary search tree and a target value, find K
  values in the BST that are closest to the target.
  Note:
  1: Given target value is a floating point.
  2: You may assume k is always valid, that is k <= total nodes.
*/
// Deque STL actually is the key to solve this problem.....
void findClosestKValues(TreeNode* root,  int target, deque& res, int k) {
  if(!root) return;
  findCloestKValues(root->left, target, res, k);
  if(res.size() < k) res.push_back(root->val);
  else if(res.size() == k) {
    if(abs(target - root->val) < abs(target - res.front())) {
      res.pop_front();
      res.push_back(root->val);
    }
  }
  findClosestKValues(root->right, target, res, k);
}

vector findClosestKValues(TreeNode* root, int target, int k) {
  deque res;
  findClosestKValues(root, target, res, k);
  vector result;
  while(!res.empty()) {
    result.push_back(res.front());
    res.pop_front();
  }
  return result;
}