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