Submission #652919

#	Time	Username	Problem	Language	Result	Execution time	Memory
652919		tamthegod	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	24 ms	31684 KiB

kangaroo

// Make the best become better
// No room for laziness
#include<bits/stdc++.h>

#define ll long long
#define int long long
#define pb push_back
#define fi first
#define se second
using namespace std;
const int maxN = 2e3 + 5;
const int mod = 1e9 + 7;
const ll oo = 1e18;
int n;
int cs, cf;
int f[maxN][maxN];
void ReadInput()
{
    cin >> n >> cs >> cf;
}
void Solve()
{
    f[0][0] = 1;
    for(int i=1; i<=n; i++)
    {
        for(int j=1; j<=n; j++)
        {
            if(i == cs || i == cf)
            {
                f[i][j] = f[i - 1][j - 1] + f[i - 1][j];
                f[i][j] %= mod;
            }
            else
            {
                f[i][j] = f[i - 1][j + 1] * j;
                f[i][j] += f[i - 1][j - 1] * (j - (i > cs) - (i > cf));
                f[i][j] %= mod;
            }
        }
    }
    cout << f[n][1];
}
int32_t main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    ReadInput();
    Solve();
}

• Subtask 1: 6 / 6
• Subtask 2: 30 / 30
• Subtask 3: 15 / 15
• Subtask 4: 49 / 49