Submission #1117758

#	Time	Username	Problem	Language	Result	Execution time	Memory
1117758		vjudge1	Kangaroo (CEOI16_kangaroo)	C++17	0 / 100	1 ms	336 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define mod 1000000007
int main(){
    int n, cs, cf, cnt = 0;
    cin>>n>>cs>>cf;
    vector<vector<vector<ll>>> dp(n + 1, vector<vector<ll>>(n + 1, vector<ll>(n + 1, 0)));
    dp[0][cf][cs] = 1;
    for (int i = 0; i < n; i++){
        if (i + 1 != cs && i + 1 != cf){
            cnt++;
        }
        for (int j = 1; j <= n; j++){
            for (int k = 1; k <= n; k++){
                int nu = i + 1;
                if (nu == cs || nu == cf){
                    dp[i + 1][j][k] = dp[i][j][k];
                    continue;
                }
                if (cnt == 1){
                    dp[i + 1][nu][nu] += dp[i][j][k];
                }
                else{
                    ll pos = max(i - 1, 0);
                    if (cnt != 2){
                        dp[i + 1][j][k] += (dp[i][j][k] * pos) % mod;
                        dp[i + 1][j][k] %= mod;
                    }
                    if (nu < min(j, cs) || nu > max(j, cs)){
                        dp[i + 1][nu][k] += dp[i][j][k];
                        dp[i + 1][nu][k] %= mod;
                    }
                    if (nu < min(k, cf) || nu > max(k, cf)){
                        dp[i + 1][j][nu] += dp[i][j][k];
                        dp[i + 1][j][nu] %= mod;
                    }
                }
            }
        }
    }
    ll ans = 0;
    for (int i = 1; i <= n; i++){
        for (int j = 1; j <= n; j++){
            ans += dp[n][i][j];
            ans %= mod;
        }
    }
    cout<<ans;
}

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