Problema
With async/await you can start several tasks and let them run at the same time. A SemaphoreSlim often caps how many run at once.
Tasks numbered 0 to n − 1 take durations[i] time units. At time 0 start as many tasks as the limit allows, in index order. Whenever tasks finish, record them (if several finish at the same moment, lower index first) and immediately start the next waiting tasks, in index order, to fill the free slots.
Implement parallel_task_order(durations, limit).
Input
durations: How long each task takes.
limit: The maximum number of tasks running at the same time.
Output
Return the task indices in the order they finish.
Restrições
1 ≤ n ≤ 100,000
1 ≤ durations[i] ≤ 10^6; 1 ≤ limit ≤ n
Exemplos
Entrada:
limit = 2
durations = [4, 2, 3, 1]
Saída esperada:
expected = [1, 0, 2, 3]Entrada:
long long limit = 2;
std::vector<long long> durations = {4, 2, 3, 1};
Saída esperada:
std::vector<long long> expected = {1, 0, 2, 3};Entrada:
long limit = 2;
long[] durations = new long[] {4, 2, 3, 1};
Saída esperada:
long[] expected = new long[] {1, 0, 2, 3};Explicação
Tasks 0 and 1 start. Task 1 ends at 2 and task 2 starts (ends at 5). Task 0 ends at 4 and task 3 starts (ends at 5). Tasks 2 and 3 finish together, lower index first: [1, 0, 2, 3].
Entrada:
limit = 3
durations = [3, 1, 2]
Saída esperada:
expected = [1, 2, 0]Entrada:
long long limit = 3;
std::vector<long long> durations = {3, 1, 2};
Saída esperada:
std::vector<long long> expected = {1, 2, 0};Entrada:
long limit = 3;
long[] durations = new long[] {3, 1, 2};
Saída esperada:
long[] expected = new long[] {1, 2, 0};Explicação
All tasks run at once and finish at 1, 2 and 3: [1, 2, 0].
Como abordar
Tente sozinho primeiro e depois abra uma dica de cada vez.
Dica 1
Keep the running tasks ordered by finish time, then by index.
Dica 2
Each step jumps to the next finish time and collects every task ending then.
Dica 3
Refill free slots with the next waiting tasks in index order.
Complexidade esperada
O(n log limit) time, O(limit) extra space
Referências
Este desafio foi adaptado para o CodeUtility. Siga o enunciado e as restrições acima.