大组合数取模模板

2019-04-14 21:59发布

站内文章 / 模拟电子
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LL n,m,p = 1e9+7; LL quick_mod(LL a, LL b) { LL ans = 1; a %= p; while(b) { if(b & 1) { ans = ans * a % p; b--; } b >>= 1; a = a * a % p; } return ans; } LL C(LL n, LL m) { if(m > n) return 0; LL ans = 1; for(int i=1; i<=m; i++) { LL a = (n + i - m) % p; LL b = i % p; ans = ans * (a * quick_mod(b, p-2) % p) % p; } return ans; } LL Lucas(LL n, LL m) { if(m == 0) return 1; return C(n % p, m % p) * Lucas(n / p, m / p) % p; } int main() { int T; scanf("%d", &T); while(T--) { scanf("%I64d%I64d", &n, &m); printf("%I64d ", Lucas(max(n,m),min(n,m))); } return 0; }

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