Submission #1115085

#	Time	Username	Problem	Language	Result	Execution time	Memory
1115085		Icelast	Kangaroo (CEOI16_kangaroo)	C++17	6 / 100	1 ms	336 KiB

kangaroo

#include <iostream>
#include <bits/stdc++.h>
#define ll long long
using namespace std;
const ll maxn = 2*1e5+5, INF = 4e18+9, mod = 1e9+7;
void solve(){
    int n, cs, cf;
    cin >> n >> cs >> cf;
    if(cs > cf) swap(cs, cf);
    vector<vector<ll>> f(n+1, vector<ll>(n+1, 0));
    f[0][0] = 1;
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= n; j++){
            if(i == cs){
                f[i][j] += f[i-1][j];
                f[i][j] += f[i-1][j-1];
                f[i][j] += 0;
            }
            if(i == cf){
                f[i][j] += f[i-1][j];
                f[i][j] += f[i-1][j-1];
                f[i][j] += 0;
            }
            if(i < cs){
                f[i][j] += 0;
                f[i][j] += f[i-1][j-1]*j;
                if(j+1 <= n) f[i][j] += f[i-1][j+1]*j;
            }
            if(cs < i && i < cf){
                f[i][j] += 0;
                f[i][j] += f[i-1][j-1]*(j-1);
                if(j+1 <= n) f[i][j] += f[i-1][j+1]*j;
            }
            if(cf < i){
                f[i][j] += 0;
                f[i][j] += f[i-1][j-1]*(j-1);
                if(j+1 <= n) f[i][j] += f[i-1][j+1]*j;
            }
            f[i][j] %= mod;
        }
    }
    cout << f[n][1];
}
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    solve();
}

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