Submission #552940

#	Time	Username	Problem	Language	Result	Execution time	Memory
552940		Jomnoi	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	33 ms	16016 KiB

kangaroo

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

const int MAX_N = 2e3 + 10;
const int MOD = 1e9 + 7;

int dp[MAX_N][MAX_N];

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int N, cs, cf;
    cin >> N >> cs >> cf;
    dp[1][1] = 1;
    for(int i = 2; i <= N; i++) {
        for(int j = 1; j <= N; j++) {
            if(i == cs or i == cf) {
                dp[i][j] = (dp[i][j] + dp[i - 1][j - 1]) % MOD;
                dp[i][j] = (dp[i][j] + dp[i - 1][j]) % MOD;
            }
            else {
                int v = j - (i > cs) - (i > cf);
                dp[i][j] = (dp[i][j] + 1ll*j * dp[i - 1][j + 1]) % MOD;
                dp[i][j] = (dp[i][j] + 1ll*v * dp[i - 1][j - 1]) % MOD;
            }
        }
    }
    cout << dp[N][1];
    return 0;
}

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