#include<bits/stdc++.h>
using namespace std;
typedef long double ld;
typedef long long ll;
#define rep(a, b) for(int a = 0; a < (b); ++a)
#define st first
#define nd second
#define pb push_back
#define all(a) a.begin(), a.end()
const ll MOD=1e9+7;
const int LIM=3e3+7;
ll dp[LIM][LIM], sil[LIM], osil[LIM];
ll pot(ll a, ll b) {
ll ans=1;
while(b) {
if(b&1) ans=(ans*a)%MOD;
a=(a*a)%MOD;
b/=2;
}
return ans;
}
ll C(ll n, ll k) {
if(k>n || n<0) return 0;
return (((sil[n]*osil[k])%MOD)*osil[n-k])%MOD;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
ll n, k;
cin >> n >> k;
sil[0]=1;
for(ll i=1; i<=n; ++i) sil[i]=(sil[i-1]*i)%MOD;
rep(i, n+1) osil[i]=pot(sil[i], MOD-2);
dp[1][1]=1;
for(int i=2; i<=n; ++i) for(ll j=1; j<=i; ++j) dp[i][j]=(dp[i-1][j]*j+dp[i-1][j-1])%MOD;
ll ans=0;
rep(i, k) {
ll x=(dp[n][k-i]*sil[k-i])%MOD;
x=(x*C(n-(k-i), i))%MOD;
if(i%2==1) x=(MOD-x)%MOD;
ans=(ans+x)%MOD;
}
cout << ans << '\n';
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
348 KB |
Output is correct |
| 2 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 3 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 4 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 5 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 6 |
Correct |
1 ms |
2392 KB |
Output is correct |
| 7 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
1 ms |
2392 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
348 KB |
Output is correct |
| 2 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 3 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 4 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 5 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 6 |
Correct |
1 ms |
2392 KB |
Output is correct |
| 7 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
1 ms |
2392 KB |
Output is correct |
| 11 |
Correct |
1 ms |
4444 KB |
Output is correct |
| 12 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 13 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 14 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 15 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 16 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 17 |
Correct |
1 ms |
6492 KB |
Output is correct |
| 18 |
Correct |
1 ms |
6492 KB |
Output is correct |
| 19 |
Correct |
1 ms |
4444 KB |
Output is correct |
| 20 |
Correct |
0 ms |
2396 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
348 KB |
Output is correct |
| 2 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 3 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 4 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 5 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 6 |
Correct |
1 ms |
2392 KB |
Output is correct |
| 7 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
1 ms |
2392 KB |
Output is correct |
| 11 |
Correct |
1 ms |
4444 KB |
Output is correct |
| 12 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 13 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 14 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 15 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 16 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 17 |
Correct |
1 ms |
6492 KB |
Output is correct |
| 18 |
Correct |
1 ms |
6492 KB |
Output is correct |
| 19 |
Correct |
1 ms |
4444 KB |
Output is correct |
| 20 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 21 |
Correct |
3 ms |
24924 KB |
Output is correct |
| 22 |
Correct |
4 ms |
24924 KB |
Output is correct |
| 23 |
Correct |
3 ms |
24924 KB |
Output is correct |
| 24 |
Correct |
3 ms |
25100 KB |
Output is correct |
| 25 |
Correct |
3 ms |
24924 KB |
Output is correct |
| 26 |
Correct |
3 ms |
25112 KB |
Output is correct |
| 27 |
Correct |
3 ms |
24924 KB |
Output is correct |
| 28 |
Correct |
2 ms |
14796 KB |
Output is correct |
| 29 |
Correct |
1 ms |
6492 KB |
Output is correct |
| 30 |
Correct |
3 ms |
24924 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
348 KB |
Output is correct |
| 2 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 3 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 4 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 5 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 6 |
Correct |
1 ms |
2392 KB |
Output is correct |
| 7 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
1 ms |
2392 KB |
Output is correct |
| 11 |
Correct |
1 ms |
4444 KB |
Output is correct |
| 12 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 13 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 14 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 15 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 16 |
Correct |
1 ms |
8540 KB |
Output is correct |
| 17 |
Correct |
1 ms |
6492 KB |
Output is correct |
| 18 |
Correct |
1 ms |
6492 KB |
Output is correct |
| 19 |
Correct |
1 ms |
4444 KB |
Output is correct |
| 20 |
Correct |
0 ms |
2396 KB |
Output is correct |
| 21 |
Correct |
3 ms |
24924 KB |
Output is correct |
| 22 |
Correct |
4 ms |
24924 KB |
Output is correct |
| 23 |
Correct |
3 ms |
24924 KB |
Output is correct |
| 24 |
Correct |
3 ms |
25100 KB |
Output is correct |
| 25 |
Correct |
3 ms |
24924 KB |
Output is correct |
| 26 |
Correct |
3 ms |
25112 KB |
Output is correct |
| 27 |
Correct |
3 ms |
24924 KB |
Output is correct |
| 28 |
Correct |
2 ms |
14796 KB |
Output is correct |
| 29 |
Correct |
1 ms |
6492 KB |
Output is correct |
| 30 |
Correct |
3 ms |
24924 KB |
Output is correct |
| 31 |
Runtime error |
97 ms |
144012 KB |
Execution killed with signal 11 |
| 32 |
Halted |
0 ms |
0 KB |
- |
