Submission #543125

#	Time	Username	Problem	Language	Result	Execution time	Memory
543125		iulia13	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	30 ms	22924 KiB

kangaroo

#include <bits/stdc++.h>

using namespace std;
const int N = 2005;
#define ll long long
const ll mod = 1e9 + 7;
void sum(ll &a, ll b)
{
    a += b;
    if (a >= mod)
        a -= mod;
}
ll dp[N][N];
int main()
{
    ll n, cs, cf;
    cin >> n >> cs >> cf;
    dp[1][1] = 1;
    for (ll i = 1; i <= n; i++)
        for (ll j = 1; j <= i; j++)
        {
            if (i == cs || i == cf)
            {
                sum(dp[i][j], dp[i - 1][j - 1]);
                sum(dp[i][j], dp[i - 1][j]);
                continue;
            }
            sum(dp[i][j], dp[i - 1][j + 1] * j % mod);
            sum(dp[i][j], (dp[i - 1][j - 1] * ((j - 2ll) + 1ll * (i < cs) + 1ll * (i < cf))) % mod);
        }
    cout << dp[n][1];
    return 0;
}

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