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1011. Capacity To Ship Packages Within D Days 👍

  • Time: $O(n\log(\Sigma |\texttt{piles[i]}|))$
  • Space: $O(1)$
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class Solution {
 public:
  int shipWithinDays(vector<int>& weights, int days) {
    int l = ranges::max(weights);
    int r = accumulate(weights.begin(), weights.end(), 0);

    while (l < r) {
      const int m = (l + r) / 2;
      if (shipDays(weights, m) <= days)
        r = m;
      else
        l = m + 1;
    }

    return l;
  }

 private:
  int shipDays(const vector<int>& weights, int shipCapacity) {
    int days = 1;
    int capacity = 0;
    for (const int weight : weights)
      if (capacity + weight > shipCapacity) {
        ++days;
        capacity = weight;
      } else {
        capacity += weight;
      }
    return days;
  };
};

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class Solution {
  public int shipWithinDays(int[] weights, int days) {
    int l = Arrays.stream(weights).max().getAsInt();
    int r = Arrays.stream(weights).sum();

    while (l < r) {
      final int m = (l + r) / 2;
      if (shipDays(weights, m) <= days)
        r = m;
      else
        l = m + 1;
    }

    return l;
  }

  private int shipDays(int[] weights, int shipCapacity) {
    int days = 1;
    int capacity = 0;
    for (final int weight : weights)
      if (capacity + weight > shipCapacity) {
        ++days;
        capacity = weight;
      } else {
        capacity += weight;
      }
    return days;
  }
}

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class Solution:
  def shipWithinDays(self, weights: list[int], days: int) -> int:
    def canShip(shipCapacity: int) -> bool:
      shipDays = 1
      capacity = 0
      for weight in weights:
        if capacity + weight > shipCapacity:
          shipDays += 1
          capacity = weight
        else:
          capacity += weight
      return shipDays <= days

    l = max(weights)
    r = sum(weights)
    return bisect.bisect_left(range(l, r), True,
                              key=lambda m: canShip(m)) + l