Submission #990941

#	Time	Username	Problem	Language	Result	Execution time	Memory
990941		vjudge1	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	21 ms	25688 KiB

kangaroo

#include<bits/stdc++.h>
#define int long long
#define _ ios::sync_with_stdio(0),cout.tie(0),cin.tie(0);
using namespace std;
const int N = 2001, M = 1e9 + 7;
int n, a, b, i, j, dp[N][N];
signed main()
{_
    cin >> n >> a >> b;  dp[1][1] = 1;
    for (i = 2; i <= n; i++)
        for (j = 1; j <= i; j++)
            if (i == a || i == b) dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j]) % M;
            else dp[i][j] = (dp[i - 1][j + 1] * j + dp[i - 1][j - 1] * (j - (a < i) - (b < i))) % M;
    return cout << dp[n][1], 0;
}

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