#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fr(m) for(int i=0; i<m; i++)
#define fro(m) for(int i=1; i<m; i++)
#define frj(m) for(int j=0; j<m; j++)
#define frr(n) for(int i=n; i>=0; i--)
#define pb push_back
#define pf push_front
#define orr ||
#define nl '\n'
#define nll cout<<'\n'
#define mod 1000000007
#define inf (1LL<<61)
#define inff (1<<30)
#define yes cout<<"YES"<<nl
#define no cout<<"NO"<<nl
#define ff first
#define ss second
#define all(v) v.begin(), v.end()
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define mxn 2005
template<int MOD>
struct ModInt {
unsigned x;
ModInt() : x(0) { }
ModInt(signed sig) : x((sig>=MOD)?sig%MOD:sig) { }
ModInt(signed long long sig) : x(sig%MOD) { }
int get() const { return (int)x; }
ModInt pow(ll p) { ModInt res = 1, a = *this; while (p) { if (p & 1) res *= a; a *= a; p >>= 1; } return res; }
ModInt &operator+=(ModInt that) { if ((x += that.x) >= MOD) x -= MOD; return *this; }
ModInt &operator-=(ModInt that) { if ((x += MOD - that.x) >= MOD) x -= MOD; return *this; }
ModInt &operator*=(ModInt that) { x = (unsigned long long)x * that.x % MOD; return *this; }
ModInt &operator/=(ModInt that) { return (*this) *= that.pow(MOD - 2); }
ModInt operator+(ModInt that) const { return ModInt(*this) += that; }
ModInt operator-(ModInt that) const { return ModInt(*this) -= that; }
ModInt operator*(ModInt that) const { return ModInt(*this) *= that; }
ModInt operator/(ModInt that) const { return ModInt(*this) /= that; }
bool operator<(ModInt that) const { return x < that.x; }
friend ostream& operator<<(ostream &os, ModInt a) { os << a.x; return os; }
friend istream& operator>>(istream &is, ModInt &a) { is >> a.x; return is; }
};
typedef ModInt<mod> mint;//change mod here
ll n, a, b;
mint dp[mxn][mxn];
int main()
{
fastio;
ifstream cin;
ofstream cout;
cin.open("kangaroo.in", ios::in);
cout.open("kangaroo.out", ios::out);
cin>>n>>a>>b;
dp[1][1]=1;
for(int i=2; i<=n; i++){
for(int j=1; j<=n; j++){
if(i==a || i==b) dp[i][j]=dp[i-1][j]+dp[i-1][j-1];
else{
//merge
dp[i][j]+=dp[i-1][j+1]*j;
//new comp
dp[i][j]+=dp[i-1][j-1]*max(0,j-(i>a)-(i>b));
}
}
}
cout<<dp[n][1]<<nl;
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
15964 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
15964 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
15964 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
15964 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
