Submission #613843

#	Time	Username	Problem	Language	Result	Execution time	Memory
613843		2fat2code	Kangaroo (CEOI16_kangaroo)	C++17	0 / 100	1 ms	340 KiB

kangaroo

#include "bits/stdc++.h"
#define fr first
#define sc second
#define all(s) s.begin(), s.end()
#define rc(s) return cout << s, 0
using namespace std;

const int mod = 1e9 + 7;
const int nmax = 2005;

int n, s, t, dp[nmax][nmax];

int32_t main(){
    ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
    //freopen("input.in", "r", stdin);
    cin >> n >> s >> t;
    if(s > t) swap(s, t);
    dp[0][0] = 1;
    for(int i=1;i<n;i++){
        for(int j=1;j<=n;j++){
            if(i < s){
                dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j + 1] * ((j + 1) * j % mod) % mod) % mod;
            }
            else if(i == s){
                dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j]) % mod;
            }
            else if(i > s && i < t){
                dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j + 1] * (j * (j - 1) % mod) % mod + dp[i - 1][j + 1] * j % mod) % mod;
            }
            else if(i == t){
                dp[i][j] = (dp[i - 1][j] + dp[i - 1][j + 1] * j % mod) % mod;
            }
            else{
                dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j + 1] * ((j + 1) * j % mod) % mod) % mod;
            }
        }
    }
    cout << dp[n - 1][1] << '\n';
}

• Subtask 1: 0 / 6
• Subtask 2: 0 / 30
• Subtask 3: 0 / 15
• Subtask 4: 0 / 49