#include <bits/stdc++.h>
#define rep(i,a,b) for(int i = a; i < b; ++i)
#define all(c) c.begin(), c.end()
#define gmax(x,y) x=max(x,y)
#define gmin(x,y) x=min(x,y)
#define gadd(x,y) x=add(x,y)
using namespace std;
typedef pair<int,int> pii;
typedef long long ll;
const int MOD = 1e9+7;
int mul(int x,int y){
return (1LL * x * y) % MOD;
}
int add(int x,int y){
int res = x + y;
while(res >= MOD)res-=MOD;
return res;
}
const int N = 3e3 + 5;
int dp[N][N];
bool vis[N][N];
int inv = (MOD+1)/2;
int gdp(int n, int m){
if(n < 0 || m < 0)return 0;
if(n == 0 || m == 0)return 1;
if(!vis[n][m]){
vis[n][m] = 1;
gadd(dp[n][m], mul(mul(m,add(m,MOD-1)),mul(gdp(n-1,m-2),inv)));
gadd(dp[n][m], mul(mul(4,m),gdp(n-1,m-1)));
gadd(dp[n][m], mul(mul(m, add(n,MOD-1)), gdp(n-2,m-1)));
gadd(dp[n][m], gdp(n-1,m));
}
return dp[n][m];
}
int main(){
cin.tie(0);
cout.tie(0);
ios_base::sync_with_stdio(0);
int n,m;
cin >> n >> m;
cout << add(gdp(n,m),MOD-1) << '\n';
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
2 ms |
376 KB |
Output is correct |
2 |
Correct |
2 ms |
376 KB |
Output is correct |
3 |
Correct |
2 ms |
632 KB |
Output is correct |
4 |
Correct |
4 ms |
1784 KB |
Output is correct |
5 |
Correct |
3 ms |
760 KB |
Output is correct |
6 |
Correct |
6 ms |
2040 KB |
Output is correct |
7 |
Correct |
3 ms |
1016 KB |
Output is correct |
8 |
Correct |
5 ms |
2168 KB |
Output is correct |
9 |
Correct |
3 ms |
1144 KB |
Output is correct |
10 |
Correct |
7 ms |
2552 KB |
Output is correct |
11 |
Correct |
0 ms |
376 KB |
Output is correct |
12 |
Correct |
11 ms |
2680 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
2 ms |
376 KB |
Output is correct |
2 |
Correct |
2 ms |
376 KB |
Output is correct |
3 |
Correct |
2 ms |
632 KB |
Output is correct |
4 |
Correct |
4 ms |
1784 KB |
Output is correct |
5 |
Correct |
3 ms |
760 KB |
Output is correct |
6 |
Correct |
6 ms |
2040 KB |
Output is correct |
7 |
Correct |
3 ms |
1016 KB |
Output is correct |
8 |
Correct |
5 ms |
2168 KB |
Output is correct |
9 |
Correct |
3 ms |
1144 KB |
Output is correct |
10 |
Correct |
7 ms |
2552 KB |
Output is correct |
11 |
Correct |
0 ms |
376 KB |
Output is correct |
12 |
Correct |
11 ms |
2680 KB |
Output is correct |
13 |
Correct |
3 ms |
248 KB |
Output is correct |
14 |
Correct |
24 ms |
16632 KB |
Output is correct |
15 |
Correct |
511 ms |
37508 KB |
Output is correct |
16 |
Correct |
7 ms |
2168 KB |
Output is correct |
17 |
Correct |
41 ms |
7160 KB |
Output is correct |
18 |
Correct |
104 ms |
12700 KB |
Output is correct |
19 |
Correct |
567 ms |
39800 KB |
Output is correct |
20 |
Correct |
444 ms |
32764 KB |
Output is correct |
21 |
Correct |
228 ms |
20984 KB |
Output is correct |
22 |
Correct |
306 ms |
26420 KB |
Output is correct |
23 |
Correct |
218 ms |
28380 KB |
Output is correct |
24 |
Correct |
743 ms |
41064 KB |
Output is correct |
25 |
Correct |
540 ms |
34860 KB |
Output is correct |
26 |
Correct |
628 ms |
38392 KB |
Output is correct |
27 |
Correct |
700 ms |
39672 KB |
Output is correct |