Submission #442056

#	Time	Username	Problem	Language	Result	Execution time	Memory
442056		JovanB	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	40 ms	16044 KiB

kangaroo

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

using ll = long long;
using ld = long double;

const int MOD = 1000000007;

int add(int a, int b){ a += b; if(a >= MOD) a -= MOD; return a; }
int mul(int a, int b){ return (1LL*a*b)%MOD; }

int dp[2005][2005];

int main(){
    ios_base::sync_with_stdio(false), cin.tie(0);
    cout.precision(10);
    cout << fixed;

    int n, a, b;
    cin >> n >> a >> b;
    dp[1][1] = 1;
    for(int i=2; i<=n; i++){
        for(int j=1; j<=n; j++){
            if(i == a || i == b) dp[i][j] = add(dp[i][j], add(dp[i-1][j-1], dp[i-1][j]));
            else{
                dp[i][j] = add(dp[i][j], mul(j, dp[i-1][j+1]));
                int mesta = j;
                if(i > a) mesta--;
                if(i > b) mesta--;
                dp[i][j] = add(dp[i][j], mul(mesta, dp[i-1][j-1]));
            }
        }
    }
    cout << dp[n][1] << "\n";
    return 0;
}

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