Minimum Elevator Rides

Each person must ride exactly once. Any group can share a ride if the sum of its weights is no greater than capacity. People may be regrouped freely; their input order does not matter. Minimize the number of rides.

Implement elevator_rides(weights, capacity).

Input

weights: The weight of each person.

capacity: The maximum combined weight in a ride.

Output

Return the minimum number of rides.

제약 조건

1 ≤ people ≤ 20. 1 ≤ capacity ≤ 1,000,000,000. Every weight is between 1 and capacity.

예시

입력:
weights = [3, 4, 5]
capacity = 7

예상 출력:
expected = 2

입력:
std::vector<long long> weights = {3, 4, 5};
long long capacity = 7;

예상 출력:
long long expected = 2;

입력:
long[] weights = new long[] {3, 4, 5};
long capacity = 7;

예상 출력:
long expected = 2;

입력:
weights = [2, 2, 2]
capacity = 6

예상 출력:
expected = 1

입력:
std::vector<long long> weights = {2, 2, 2};
long long capacity = 6;

예상 출력:
long long expected = 1;

입력:
long[] weights = new long[] {2, 2, 2};
long capacity = 6;

예상 출력:
long expected = 1;

참고 자료

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• Elevator Rides — 1653