Codeforces Round #258 (Div. 2)Devu and Flowers 容斥原理_html/css_WEB-ITnose

题目： Codeforces Round #258 (Div. 2)Devu and Flowers 题意：n个boxes ，第i个box有fi个flowers，每个boxes中的flowers完全相同，不同boxes的flowers不同，求从n个boxes中取出s个flowers的方案数。n#include using namespace std;const int MOD = 1e9 + 7;typedef long long LL;LL invv[25];LL inv(LL x)/// 求逆元{ return x == 1 ? 1LL : (MOD - MOD / x) * inv (MOD % x) % MOD;}LL Cmn(LL n, LL m) ///求组合数{ LL ret = 1; for (int i = 1; i > n >> s; for (int i = 0; i > a[i]; int ALL = (1