Submission #878417

#	Time	Username	Problem	Language	Result	Execution time	Memory
878417		pemguimn	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	15 ms	23132 KiB

kangaroo

#include <bits/stdc++.h>
#define int long long
#define pii pair<int, int>
#define pb push_back
#define gcd __gcd
#define endl "\n"
#define task "hihi"
using namespace std;
const int N = 2e3 + 5, MOD = 1e9 + 7;  
int dp[N][N];
signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    //freopen(task".inp", "r", stdin);
    //freopen(task".out", "w", stdout);
    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];
    return 0;
}

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