Submission #849655

#	Time	Username	Problem	Language	Result	Execution time	Memory
849655		thanh913	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	14 ms	31836 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
using ll = long long;

const int N = 2e3+5, mod = 1e9+7;

//--------------------------------------
int n, st, ed;
ll f[N][N];

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    cin >> n >> st >> ed;
    f[1][1] = 1;
    for (int i = 2; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            if (i == st || i == ed) {
                f[i][j] = f[i-1][j-1] + f[i-1][j];
            }
            else {
                f[i][j] = f[i-1][j-1] * (j - (i > st) - (i > ed));
                f[i][j] += f[i-1][j+1] * j;
            }
            f[i][j] %= mod;
        }
    }
    cout << f[n][1];
}

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