hdu 5407 CRB and Candies（数论）

题目链接：hdu 5407 CRB and Candies

ans = LCM(1~N+1) / (N+1) % mod

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
typedef long long ll;
const int maxn = 1e6 + 5;
const int mod = 1000000007;

int nc, vis[maxn], fac[maxn], F[maxn];

void preserve () {
nc = 0;
for (int i = 2; i < maxn; i++) {
if (vis[i]) continue;
fac[nc++] = i;
for (int j = i + i; j < maxn; j += i)
vis[j] = 1;
}

for (int i = 0; i < nc; i++) {
ll k = fac[i];
while (k < maxn) {
vis[k] = fac[i];
k *= fac[i];
}
}

F[1] = 1;
for (int i = 2; i < maxn; i++)
F[i] = 1LL * F[i-1] * vis[i] % mod;
}

int pow_mod(ll x, int n) {
ll ret = 1;
while (n) {
if (n&1)
ret = ret * x % mod;
x = x * x % mod;
n >>= 1;
}
return ret;
}

int inv(ll x) {
return pow_mod(x, mod-2);
}

int main () {
preserve ();
int cas, n;
scanf("%d", &cas);
while (cas--) {
scanf("%d", &n);
// printf("%d! %lld\n", F[n+1], inv(n+1));
printf("%lld\n", 1LL * F[n+1] * inv(n+1) % mod);
}
return 0;
}