Submission #946630

#	Time	Username	Problem	Language	Result	Execution time	Memory
946630		vjudge1	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	16 ms	16272 KiB

kangaroo

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

using LL = long long;
using PII = pair<int, int>;

const int N = 4000;
const int M = 1e9 + 7;
int dp[N][N];

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    int n, cs, cf;
    cin >> n >> cs >> cf;

    dp[1][1] = 1;

    for(int i = 2; i <= n; ++i){
        for(int j = 1; j <= i; ++j){
            if(i == cs or i == cf) dp[i][j] = dp[i - 1][j] + dp[i - 1][j - 1];
            else {
                dp[i][j] += 1LL * dp[i - 1][j + 1] * j % M ;                          //merging of two component
                dp[i][j] += 1LL * dp[i - 1][j - 1] * (j-2 + (i < cf) + (i < cs)) % M; // start of a new component
            }
            dp[i][j] %= M;
        } 
    }

    cout << dp[n][1]<<"\n";
}

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