Divide and Sum CodeForces - 1445D（排列组合+逆元）题意：题目：分析：AC代码：
题意：给定一个长度为2n的数组，将数组分成两个长度为n的数组p,q，将p从小到大排序，将q从大到小排序，对于每种分法，f(p,q)=∑i=1n\sum_{i=1}^{n}∑i=1n|xi−yi|.求总和题目：You are given an array a of length 2n. Consider a partition of array a into two subsequences p and q of length n each (each element of array a sh
