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

September LeetCoding Challenge 11

Description

Group the People Given the Group Size They Belong To

There are n people that are split into some unknown number of groups. Each person is labeled with a unique ID from 0 to n - 1.

You are given an integer array groupSizes, where groupSizes[i] is the size of the group that person i is in. For example, if groupSizes[1] = 3, then person 1 must be in a group of size 3.

Return a list of groups such that each person i is in a group of size groupSizes[i].

Each person should appear in exactly one group, and every person must be in a group. If there are multiple answers, return any of them. It is guaranteed that there will be at least one valid solution for the given input.

Example 1:

Input: groupSizes = [3,3,3,3,3,1,3]
Output: [[5],[0,1,2],[3,4,6]]
Explanation: 
The first group is [5]. The size is 1, and groupSizes[5] = 1.
The second group is [0,1,2]. The size is 3, and groupSizes[0] = groupSizes[1] = groupSizes[2] = 3.
The third group is [3,4,6]. The size is 3, and groupSizes[3] = groupSizes[4] = groupSizes[6] = 3.
Other possible solutions are [[2,1,6],[5],[0,4,3]] and [[5],[0,6,2],[4,3,1]].

Example 2:

Input: groupSizes = [2,1,3,3,3,2]
Output: [[1],[0,5],[2,3,4]]

Constraints:

• groupSizes.length == n
• 1 <= n <= 500
• 1 <= groupSizes[i] <= n

Solution

class Solution {
public:
  vector<vector<int>> groupThePeople(vector<int>& groupSizes) {
    unordered_map<int, vector<int>> mp;
    for(int i = 0; i < groupSizes.size(); ++i) {
      mp[groupSizes[i]].push_back(i);
    }

    vector<vector<int>> answer;
    for(auto &[sz, people] : mp) {
      for(int i = 0; i * sz < people.size(); ++i) {
        vector<int> result;
        for(int j = 0; j < sz; ++j) {
          result.push_back(people[i * sz + j]);
        }
        answer.emplace_back(move(result));
      }
    }

    return answer;
  }
};

// Accepted
// 103/103 cases passed (11 ms)
// Your runtime beats 57.7 % of cpp submissions
// Your memory usage beats 46.45 % of cpp submissions (13.2 MB)