# 2244. Minimum Rounds to Complete All Tasks      • Time: $O(n)$
• Space: $O(n)$
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 class Solution { public: int minimumRounds(vector& tasks) { int ans = 0; unordered_map count; for (const int task : tasks) ++count[task]; // freq = 1 -> impossible // freq = 2 -> needs 1 round // freq = 3 -> needs 1 round // freq = 3k -> needs k rounds // freq = 3k + 1 = 3 * (k - 1) + 2 * 2 -> needs k + 1 rounds // freq = 3k + 2 = 3 * k + 2 * 1 -> needs k + 1 rounds for (const auto& [_, freq] : count) if (freq == 1) return -1; else ans += (freq + 2) / 3; return ans; } }; 
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 class Solution { public int minimumRounds(int[] tasks) { int ans = 0; Map count = new HashMap<>(); for (final int task : tasks) count.merge(task, 1, Integer::sum); // freq = 1 -> impossible // freq = 2 -> needs 1 round // freq = 3 -> needs 1 round // freq = 3k -> needs k rounds // freq = 3k + 1 = 3 * (k - 1) + 2 * 2 -> needs k + 1 rounds // freq = 3k + 2 = 3 * k + 2 * 1 -> needs k + 1 rounds for (final int freq : count.values()) if (freq == 1) return -1; else ans += (freq + 2) / 3; return ans; } } 
 1 2 3 4 class Solution: def minimumRounds(self, tasks: List[int]) -> int: freqs = Counter(tasks).values() return -1 if 1 in freqs else sum((f + 2) // 3 for f in freqs)