Consider a group of N students and P courses. Each student visits zero, one or more than one courses. Your task is to determine whether it is possible to form a committee of exactly P students that satisfies simultaneously the conditions:
A factory produces products packed in square packets of the same height h and of the sizes 1*1, 2*2, 3*3, 4*4, 5*5, 6*6. These products are always delivered to customers in the square parcels of the same height h as the products have and of the size 6*6. Because of the expenses it is the interest of the factory as well as of the customer to minimize the number of parcels necessary to deliver the ordered products from the factory to the customer. A good program solving the problem of finding the minimal number of parcels necessary to deliver the given products according to an order would save a lot of money. You are asked to make such a program.
你正在安装一个广告牌，并希望它高度最大。这块广告牌将有两个钢制支架，两边各一个。每个钢支架的高度必须相等。
你有一堆可以焊接在一起的钢筋 rods。举个例子，如果钢筋的长度为 1、2 和 3，则可以将它们焊接在一起形成长度为 6 的支架。
返回广告牌的最大可能安装高度。如果没法安装广告牌，请返回 0。
来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/tallest-billboard
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剪枝：
Newman likes playing with cats. He possesses lots of cats in his home. Because the number of cats is really huge, Newman wants to group some of the cats. To do that, he first offers a number to each of the cat (1, 2, 3, …, n). Then he occasionally combines the group cat i is in and the group cat j is in, thus creating a new group. On top of that, Newman wants to know the size of the k-th biggest group at any time. So, being a friend of Newman, can you help him?
要点:
树状数组中寻找第K大元素
2985.The k-th Largest Group.cpp
给定一个整数数组 nums，返回区间和在 [lower, upper] 之间的个数，包含 lower 和 upper。
区间和 S(i, j) 表示在 nums 中，位置从 i 到 j 的元素之和，包含 i 和 j (i ≤ j)。
说明:
最直观的算法复杂度是 O(n2) ，请在此基础上优化你的算法。
来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/count-of-range-sum
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
给定一个整数数组 nums，按要求返回一个新数组 counts。数组 counts 有该性质： counts[i] 的值是 nums[i] 右侧小于 nums[i] 的元素的数量。
来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/count-of-smaller-numbers-after-self
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
树状数组用来求区间索引的计数和