2244. Minimum Rounds to Complete All Tasks

You are given a 0-indexed integer array tasks, where tasks[i] represents the difficulty level of a task. In each round, you can complete either 2 or 3 tasks of the same difficulty level.

Return the minimum rounds required to complete all the tasks, or -1 if it is not possible to complete all the tasks.

class Solution {
public:
    int minimumRounds(vector<int>& tasks) {
        unordered_map<int, int> mp;
        for(auto& t : tasks)
            mp[t]++;
        int res = 0;
        for(auto& [k, v] : mp) {
            if(v == 1) return -1;
            res += v / 3 + ((v % 3) > 0);
        }
        return res;
    }
};