Submission #9116

#	Time	Username	Problem	Language	Result	Execution time	Memory
9116		kcm1700	Actual visible points (kriii2_AC)	C++14	0 / 4	12 ms	6748 KiB

AC

#include <cstdio>
#include <set>
#include <algorithm>

using namespace std;

int n,m;

const int mod = 1000000007;
long long fact[203000];
long long ifact[203000];
long long invs[203000];

long long counts[100003];

int main(){
  invs[1] = 1;
  for(int i = 2; i <= 200010; i++) invs[i] = (invs[mod%i] * (mod-mod/i)) % mod;
  fact[0] = 1;
  for(int i = 1; i <= 200010; i++) fact[i] = i * fact[i-1] % mod;
  ifact[0] = 1;
  for(int i = 1; i <= 200010; i++) ifact[i] = (invs[i] * ifact[i-1]) % mod;

  scanf("%d%d",&n,&m);
  set<int> xs;
  for(int i = 0; i < m; i++) {
    int x;
    scanf("%d",&x);
    xs.insert(x);
  }
  long long ans = 0;
  for(int i = 1; i <= 100000; i++) {
    counts[i] += fact[i+(n-2)] * ifact[n-1] % mod * ifact[i-1] % mod;
    counts[i] %= mod;
    if (xs.count(i) == 0) continue;
    ans += counts[i];
    for(int j = i*2; j <= 100000; j += i) {
      counts[j] -= counts[i];
    }
  }
  ans %= mod;
  ans += mod;
  ans %= mod;
  printf("%lld\n", ans);
  return 0;
}

• Subtask 1: 0 / 1
• Subtask 2: 0 / 3