Submission #604888

#	Time	Username	Problem	Language	Result	Execution time	Memory
604888		Vanilla	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	26 ms	22972 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
typedef long long int64;
const int maxn = 2e3 + 2;
const int64 mod = 1e9 + 7;
int64 dp[maxn][maxn];

int main() {
    int n,a,b;
    cin >> n >> a >> b;
    dp[0][0] = 1;
    for (int64 i = 1; i <= n; i++){
        for (int64 j = 1; j <= i; j++){
            if (i == a || i == b) {
                dp[i][j] = (dp[i-1][j-1] + dp[i-1][j]) % mod;
            }
            else {
                dp[i][j] = (dp[i-1][j + 1] * j % mod + dp[i-1][j-1] * (j - (i > a) - (i > b)) % mod) % mod;
            }
        }
    }
    cout << dp[n][1];
    return 0;
}

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