Submission #1174882

#	Time	Username	Problem	Language	Result	Execution time	Memory
1174882		nguyenkhangninh99	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	29 ms	23112 KiB

kangaroo

#include <bits/stdc++.h>

using namespace std;

#define int long long

const int maxn = 2e3 + 5, mod = 1e9 + 7;  
int dp[maxn][maxn];
signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);

        int n, cs, cf; cin >> n >> cs >> cf;
    dp[1][1] = 1;
    for(int i = 1; i < n; i++){
        for(int j = 1; j <= i; j++){
            if(i + 1 == cs || i + 1 == cf){
                (dp[i + 1][j] += dp[i][j]) %= mod;
                (dp[i + 1][j + 1] += dp[i][j]) %= mod;
            }  else{
                (dp[i + 1][j - 1] += dp[i][j] * (j - 1)) %= mod;
                (dp[i + 1][j + 1] += dp[i][j] * (j + 1 - (i + 1 > cs) - (i + 1 > cf))) %= mod;
            }
        }
    }
    cout << dp[n][1];
}

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