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1231. Divide Chocolate 👍

  • Time: $O(n\log(\Sigma |\texttt{sweetness[i]}|))$
  • Space: $O(1)$
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class Solution {
 public:
  int maximizeSweetness(vector<int>& sweetness, int k) {
    int l = sweetness.size() / (k + 1);
    int r = accumulate(sweetness.begin(), sweetness.end(), 0) / (k + 1);

    while (l < r) {
      const int m = (l + r) / 2;
      if (canEat(sweetness, k, m))
        l = m + 1;
      else
        r = m;
    }

    return canEat(sweetness, k, l) ? l : l - 1;
  }

 private:
  // Returns true if can eat m sweetness (the minimum sweetness of each piece).
  bool canEat(const vector<int>& sweetness, int k, int m) {
    int pieces = 0;
    int sum = 0;  // the running sum

    for (const int s : sweetness) {
      sum += s;
      if (sum >= m) {
        if (++pieces > k)
          return true;
        sum = 0;
      }
    }

    return false;
  };
};

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class Solution {
  public int maximizeSweetness(int[] sweetness, int k) {
    int l = sweetness.length / (k + 1);
    int r = Arrays.stream(sweetness).sum() / (k + 1);

    while (l < r) {
      final int m = (l + r) / 2;
      if (canEat(sweetness, k, m))
        l = m + 1;
      else
        r = m;
    }

    return canEat(sweetness, k, l) ? l : l - 1;
  }

  // Returns true if can eat m sweetness (the minimum sweetness of each piece).
  private boolean canEat(int[] sweetness, int k, int m) {
    int pieces = 0;
    int sum = 0; // the running sum

    for (final int s : sweetness) {
      sum += s;
      if (sum >= m) {
        if (++pieces > k)
          return true;
        sum = 0;
      }
    }

    return false;
  }
}

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class Solution:
  def maximizeSweetness(self, sweetness: List[int], k: int) -> int:
    l = len(sweetness) // (k + 1)
    r = sum(sweetness) // (k + 1)

    def canEat(m: int) -> bool:
      """
      Returns True if can eat m sweetness (the minimum sweetness of each piece).
      """
      pieces = 0
      summ = 0  # the running sum
      for s in sweetness:
        summ += s
        if summ >= m:
          pieces += 1
          summ = 0
      return pieces > k

    while l < r:
      m = (l + r) // 2
      if canEat(m):
        l = m + 1
      else:
        r = m

    return l if canEat(l) else l - 1