Today I have done leetcode's December LeetCoding Challenge with cpp.

December LeetCoding Challenge 28

Description

Remove Stones to Minimize the Total

You are given a 0-indexed integer array piles, where piles[i] represents the number of stones in the ith pile, and an integer k. You should apply the following operation exactly k times:

• Choose any piles[i] and remove floor(piles[i] / 2) stones from it.

Notice that you can apply the operation on the same pile more than once.

Return the minimum possible total number of stones remaining after applying the k operations.

floor(x) is the greatest integer that is smaller than or equal to x (i.e., rounds x down).

Example 1:

Input: piles = [5,4,9], k = 2
Output: 12
Explanation: Steps of a possible scenario are:
- Apply the operation on pile 2. The resulting piles are [5,4,5].
- Apply the operation on pile 0. The resulting piles are [3,4,5].
The total number of stones in [3,4,5] is 12.

Example 2:

Input: piles = [4,3,6,7], k = 3
Output: 12
Explanation: Steps of a possible scenario are:
- Apply the operation on pile 2. The resulting piles are [4,3,3,7].
- Apply the operation on pile 3. The resulting piles are [4,3,3,4].
- Apply the operation on pile 0. The resulting piles are [2,3,3,4].
The total number of stones in [2,3,3,4] is 12.

Constraints:

• 1 <= piles.length <= 105
• 1 <= piles[i] <= 104
• 1 <= k <= 105

Solution

class Solution {
public:
  int minStoneSum(vector<int>& piles, int k) {
    map<int, int, greater<int>> count;
    int answer = 0;
    for(auto pile : piles) {
      count[pile] += 1;
      answer += pile;
    }
    while(k) {
      auto it = count.begin();
      if(it->first < 2) break;
      if(k > it->second) {
        answer -= (it->first / 2) * it->second;
        count[it->first - it->first / 2] += it->second;
        k -= it->second;
        count.erase(it);
      } else {
        answer -= (it->first / 2) * k;
        k = 0;
      }
    }
    return answer;
  }
};

// Accepted
// 59/59 cases passed (352 ms)
// Your runtime beats 99.48 % of cpp submissions
// Your memory usage beats 5 % of cpp submissions (107.8 MB)