#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#define pb push_back
#define F first
#define S second
#define all(a) a.begin(),a.end()
#define pii pair <int,int>
#define PII pair<pii , pii>
#define ld long double
#define int long long
#define sz(v) (int)v.size()
#define rep(i , a , b) for(int i=a;i <= (b);i++)
#define per(i , a , b) for(int i=a;i >= (b);i--)
using namespace std ;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int maxn = 100 , maxw= 1e3 + 10, lg = 18 , inf = 1e18 , mod= 1e9 + 7 ;
int dp2[maxn][maxn] , dp[maxn][maxn] , f[maxn] , inv[maxn] , pr[maxn] , a[maxn] , sm[maxn][maxn] ;
int po(int a, int b){
if(b==0)return 1;
int v =po(a,b/2) ;
v = v*v%mod ;
if(b&1) v =v*a %mod ;
return v;
}
int c(int n , int k){
if(n < k || k < 0)return 0 ;
return f[n] * inv[k]%mod * inv[n-k]%mod ;
}
signed main(){
ios::sync_with_stdio(0);cin.tie(0);
f[0] = 1;
rep(i , 1, maxn-1){
f[i] = f[i-1] * i % mod ;
}
inv[maxn-1] = po(f[maxn-1] , mod-2);
per(i , maxn-2 , 0){
inv[i] = inv[i+1] * (i+1) % mod ;
}
int n;cin >> n ;
rep(i , 1, n){
cin >> a[i] ;
}
pr[0] = a[1] -1 ;
rep(i , 1, n){
pr[i] = pr[i-1] + (a[i+1] - a[i] - 1) ;
}
int a2 = po(2, mod-2);
dp2[1][0] = 1; dp2[1][1] = a2 ;
rep(i , 1 , n){
rep(j , 1, n){
dp2[i+1][j+1] = (dp2[i+1][j+1] + a2*dp2[i][j] %mod)%mod ;
dp2[i+1][j-1] = (dp2[i+1][j-1] + a2*dp2[i][j]%mod)%mod ;
dp2[i+1][j] = (dp2[i+1][j] + dp2[i][j]%mod)%mod ;
}
}
dp[0][0]= 1;
rep(i , 0, n){
rep(j , 1, i+2){
sm[i][j] = (sm[i][j] + sm[i][j-1])%mod ;
}
rep(j , 0 , i){
dp[i][j] = (dp[i][j] + sm[i][j] * inv[i-j]%mod)%mod ;
rep(k , 1 , n-i){
int x = dp[i][j] * c(pr[j]-(i) , k) %mod * f[k] % mod * dp2[k][0] %mod ;
dp[i+k][j] = (dp[i+k][j] + x) %mod ;
x = x * k%mod * f[i+k-1-j]%mod ;
sm[i+k][j] = (sm[i+k][j] + x)%mod ;
dp[i+k][j] = (dp[i+k][j]-x*inv[i+k-j]%mod+mod)%mod ;
}
}
}
cout << dp[n][n]%mod << "\n";
}
/*
*/
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
348 KB |
Output is correct |
2 |
Correct |
0 ms |
348 KB |
Output is correct |
3 |
Correct |
0 ms |
348 KB |
Output is correct |
4 |
Correct |
0 ms |
348 KB |
Output is correct |
5 |
Correct |
0 ms |
348 KB |
Output is correct |
6 |
Correct |
0 ms |
348 KB |
Output is correct |
7 |
Correct |
0 ms |
344 KB |
Output is correct |
8 |
Correct |
1 ms |
348 KB |
Output is correct |
9 |
Correct |
1 ms |
348 KB |
Output is correct |
10 |
Correct |
0 ms |
348 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
348 KB |
Output is correct |
2 |
Correct |
0 ms |
348 KB |
Output is correct |
3 |
Correct |
0 ms |
348 KB |
Output is correct |
4 |
Correct |
0 ms |
348 KB |
Output is correct |
5 |
Correct |
0 ms |
348 KB |
Output is correct |
6 |
Correct |
0 ms |
348 KB |
Output is correct |
7 |
Correct |
0 ms |
344 KB |
Output is correct |
8 |
Correct |
1 ms |
348 KB |
Output is correct |
9 |
Correct |
1 ms |
348 KB |
Output is correct |
10 |
Correct |
0 ms |
348 KB |
Output is correct |
11 |
Correct |
1 ms |
604 KB |
Output is correct |
12 |
Correct |
1 ms |
604 KB |
Output is correct |
13 |
Correct |
1 ms |
600 KB |
Output is correct |
14 |
Correct |
1 ms |
604 KB |
Output is correct |
15 |
Correct |
1 ms |
604 KB |
Output is correct |
16 |
Correct |
1 ms |
604 KB |
Output is correct |
17 |
Correct |
1 ms |
604 KB |
Output is correct |
18 |
Correct |
2 ms |
600 KB |
Output is correct |
19 |
Correct |
2 ms |
600 KB |
Output is correct |
20 |
Correct |
2 ms |
600 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
348 KB |
Output is correct |
2 |
Correct |
0 ms |
348 KB |
Output is correct |
3 |
Correct |
0 ms |
348 KB |
Output is correct |
4 |
Correct |
0 ms |
348 KB |
Output is correct |
5 |
Correct |
0 ms |
348 KB |
Output is correct |
6 |
Correct |
0 ms |
348 KB |
Output is correct |
7 |
Correct |
0 ms |
344 KB |
Output is correct |
8 |
Correct |
1 ms |
348 KB |
Output is correct |
9 |
Correct |
1 ms |
348 KB |
Output is correct |
10 |
Correct |
0 ms |
348 KB |
Output is correct |
11 |
Correct |
1 ms |
604 KB |
Output is correct |
12 |
Correct |
1 ms |
604 KB |
Output is correct |
13 |
Correct |
1 ms |
600 KB |
Output is correct |
14 |
Correct |
1 ms |
604 KB |
Output is correct |
15 |
Correct |
1 ms |
604 KB |
Output is correct |
16 |
Correct |
1 ms |
604 KB |
Output is correct |
17 |
Correct |
1 ms |
604 KB |
Output is correct |
18 |
Correct |
2 ms |
600 KB |
Output is correct |
19 |
Correct |
2 ms |
600 KB |
Output is correct |
20 |
Correct |
2 ms |
600 KB |
Output is correct |
21 |
Runtime error |
2 ms |
600 KB |
Execution killed with signal 11 |
22 |
Halted |
0 ms |
0 KB |
- |