Leetcode 1482

   /**
     * @param bloomDay 什么时候开花
     * @param m        m束
     * @param k        k朵花做成一束
     * @return
     */
    public static int minDays(int[] bloomDay, int m, int k) {
        int n = bloomDay.length;
        if (n < m * k)//不够花束
            return -1;

        int low = Integer.MAX_VALUE, high = 0;
        for (int i = 0; i < n; i++) {
            low = Math.min(low, bloomDay[i]);//找到最小值作为low
            high = Math.max(high, bloomDay[i]);//找到最大值作为high
        }
        while (low < high) {//不断靠近目标值,当low = high时，此时即为最少天数
            int days = (high - low) / 2 + low;
            if (canMake(bloomDay, days, m, k)) {
                high = days;
            } else {
                low = days + 1;
            }
        }
        return low;
    }

	//辅助函数，找到临界点
    public static boolean canMake(int[] bloomDay, int days, int m, int k) {
        //在确保可以制作出指定数量的花束的情况下，所需的最少天数一定会大于min，小于max
        //days很小的时候，总是返回false，不够做够花束，而days很大的时候，则总是返回true
        int bouquets = 0;
        int flowers = 0;
        int length = bloomDay.length;
        for (int i = 0; i < length && bouquets < m; i++) {
            if (bloomDay[i] <= days) {
                flowers++;
                if (flowers == k) {
                    bouquets++;
                    flowers = 0;
                }
            } else {
                flowers = 0;
            }
        }
        return bouquets >= m;
    }