LC *1011. 在 D 天内送达包裹的能力（二分）

class Solution {
public:
    int shipWithinDays(vector<int>& weights, int D) {
        int left = 0, right = 0;
        for (int w : weights) {
            left = max(left, w);
            right += w;
        }
        while (left < right) {
            int mid = (left + right) / 2;
            int day = 1, num = 0;
            for (int w : weights) {
                if (num + w > mid) {
                    day++;
                    num = 0;
                }
                num += w;
            }
            if (day > D) {
                left = mid + 1;
            }
            else {
                right = mid;
            }
        }
        return left;
    }
};