#include <bits/stdc++.h>
#define ld long double
#define endl "\n"
#define fastio ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define pb(x) push_back(x)
#define mp(a,b) make_pair(a,b)
#define ms(v,x) memset(v,x,sizeof(v))
#define all(v) v.begin(),v.end()
#define ff first
#define ss second
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define per(i, a, b) for(int i = b-1; i>=a ; i--)
#define trav(a, x) for(auto& a : x)
#define allin(a , x) for(auto a : x)
#define td(v) v.begin(),v.end()
#define sz(v) (int)v.size()
//#define int long long
using namespace std;
typedef vector<int> vi;
#define y1 abacaba
#define left sefude
#define db(x) cerr << #x <<" == "<<x << endl;
#define db2(x,y) cerr<<#x <<" == "<<x<<", "<<#y<<" == "<<y<<endl;
typedef long long ll;
typedef pair<int,int> pii;
inline ll mod(ll n, ll m ){ ll ret = n%m; if(ret < 0) ret += m; return ret; }
ll gcd(ll a, ll b){return (b == 0LL ? a : gcd(b, a%b));}
ll exp(ll a,ll b,ll m){
if(b==0LL) return 1LL;
if(b==1LL) return mod(a,m);
ll k = mod(exp(a,b/2,m),m);
if(b&1LL){
return mod(a*mod(k*k,m),m);
}
else return mod(k*k,m);
}
int n;
const int N = 2020;
const int M = 1e9 + 7;
ll dp[N][N];
int cs,cf;
ll C(int j){
return (1ll*j*(j-1)/2)%M;
}
ll solve(int i,int j){// to em i em tem j componentes
if(j < 0)return 0;
ll &x = dp[i][j];
if(x!=-1)return x;
x = 0;
int bad = (i>=cs) + (i>=cf);
if(i == n + 1){
return x = (j == 1);
}
if(i == cs || i == cf){
return x = (solve(i+1,j) + solve(i+1,j+1))%M;
}
// tem j+1 gaps pra criar um cara, mas n pode usar o start/end
x = (x + 1ll*solve(i+1,j+1)*(j + 1 - bad))%M;
// pode juntar o (1,2) ou (2,3) ... (j-1,j)
x = (x + solve(i+1,j-1)*(j-1));
return mod(x,M);
}
int32_t main(){
fastio;
cin >> n;
cin >> cs >> cf;
ms(dp,-1);
cout << solve(2,1) << endl;
// math -> gcd it all
// Did u check N=1? Did you switch N,M?
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
17 ms |
32280 KB |
Output is correct |
2 |
Correct |
22 ms |
32256 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
17 ms |
32280 KB |
Output is correct |
2 |
Correct |
22 ms |
32256 KB |
Output is correct |
3 |
Correct |
22 ms |
32256 KB |
Output is correct |
4 |
Correct |
15 ms |
32256 KB |
Output is correct |
5 |
Correct |
19 ms |
32256 KB |
Output is correct |
6 |
Correct |
15 ms |
32256 KB |
Output is correct |
7 |
Correct |
22 ms |
32256 KB |
Output is correct |
8 |
Correct |
15 ms |
32256 KB |
Output is correct |
9 |
Correct |
15 ms |
32256 KB |
Output is correct |
10 |
Correct |
16 ms |
32256 KB |
Output is correct |
11 |
Correct |
16 ms |
32256 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
17 ms |
32280 KB |
Output is correct |
2 |
Correct |
22 ms |
32256 KB |
Output is correct |
3 |
Correct |
22 ms |
32256 KB |
Output is correct |
4 |
Correct |
15 ms |
32256 KB |
Output is correct |
5 |
Correct |
19 ms |
32256 KB |
Output is correct |
6 |
Correct |
15 ms |
32256 KB |
Output is correct |
7 |
Correct |
22 ms |
32256 KB |
Output is correct |
8 |
Correct |
15 ms |
32256 KB |
Output is correct |
9 |
Correct |
15 ms |
32256 KB |
Output is correct |
10 |
Correct |
16 ms |
32256 KB |
Output is correct |
11 |
Correct |
16 ms |
32256 KB |
Output is correct |
12 |
Correct |
15 ms |
32256 KB |
Output is correct |
13 |
Correct |
16 ms |
32256 KB |
Output is correct |
14 |
Correct |
16 ms |
32256 KB |
Output is correct |
15 |
Correct |
16 ms |
32336 KB |
Output is correct |
16 |
Correct |
16 ms |
32256 KB |
Output is correct |
17 |
Correct |
17 ms |
32256 KB |
Output is correct |
18 |
Correct |
16 ms |
32256 KB |
Output is correct |
19 |
Correct |
16 ms |
32256 KB |
Output is correct |
20 |
Correct |
16 ms |
32256 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
17 ms |
32280 KB |
Output is correct |
2 |
Correct |
22 ms |
32256 KB |
Output is correct |
3 |
Correct |
22 ms |
32256 KB |
Output is correct |
4 |
Correct |
15 ms |
32256 KB |
Output is correct |
5 |
Correct |
19 ms |
32256 KB |
Output is correct |
6 |
Correct |
15 ms |
32256 KB |
Output is correct |
7 |
Correct |
22 ms |
32256 KB |
Output is correct |
8 |
Correct |
15 ms |
32256 KB |
Output is correct |
9 |
Correct |
15 ms |
32256 KB |
Output is correct |
10 |
Correct |
16 ms |
32256 KB |
Output is correct |
11 |
Correct |
16 ms |
32256 KB |
Output is correct |
12 |
Correct |
15 ms |
32256 KB |
Output is correct |
13 |
Correct |
16 ms |
32256 KB |
Output is correct |
14 |
Correct |
16 ms |
32256 KB |
Output is correct |
15 |
Correct |
16 ms |
32336 KB |
Output is correct |
16 |
Correct |
16 ms |
32256 KB |
Output is correct |
17 |
Correct |
17 ms |
32256 KB |
Output is correct |
18 |
Correct |
16 ms |
32256 KB |
Output is correct |
19 |
Correct |
16 ms |
32256 KB |
Output is correct |
20 |
Correct |
16 ms |
32256 KB |
Output is correct |
21 |
Correct |
19 ms |
32256 KB |
Output is correct |
22 |
Correct |
20 ms |
32256 KB |
Output is correct |
23 |
Correct |
20 ms |
32384 KB |
Output is correct |
24 |
Correct |
56 ms |
32384 KB |
Output is correct |
25 |
Correct |
51 ms |
32384 KB |
Output is correct |
26 |
Correct |
52 ms |
32384 KB |
Output is correct |
27 |
Correct |
60 ms |
32384 KB |
Output is correct |
28 |
Correct |
35 ms |
32384 KB |
Output is correct |