Submission #158089

#	Time	Username	Problem	Language	Result	Execution time	Memory
158089		solimm4sks	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	36 ms	16120 KiB

kangaroo

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

int dp[2005][2005];
const int MOD = 1e9 + 7;

int main()
{
    int n, cs, cf;
    cin >> n >> cs >> cf;
    dp[0][0] = 1;
    for(int i = 1; i <= n; ++i){
        for(int j = 1; j <= n; ++j){
            if(i == cs || i == cf){ ///must put this at beggining or end
                dp[i][j] = dp[i - 1][j] + dp[i - 1][j - 1]; ///(will link/wont link chain)
                dp[i][j] %= MOD;
            }else{
                dp[i][j] = (1LL * dp[i - 1][j + 1] * j) % MOD + (1LL * dp[i - 1][j - 1] * (j - (i > cs) - (i > cf))) % MOD; ///if i > cs I cant put it before cs, if i > cf then I cant put it after it
                dp[i][j] %= MOD;
            }
        }
    }

    cout << dp[n][1] << "\n";
    return 0;
}

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