Submission #1051154

#	Time	Username	Problem	Language	Result	Execution time	Memory
1051154		SulA	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	22 ms	31752 KiB

kangaroo

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    int n, cs, cf; cin >> n >> cs >> cf;
    const int MOD = 1e9 + 7;
    long long dp[n+1][n+1] = {};
    dp[0][0] = 1;

    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= i; j++) {
            if (i == cs || i == cf) {
                dp[i][j] = dp[i-1][j] + dp[i-1][j-1];
            } else {
                dp[i][j] = (
                        dp[i-1][j-1]*(j - (cs < i) - (cf < i)) +
                        dp[i-1][j+1]*j % MOD
                        ) % MOD;
            }
        }
    }
    cout << dp[n][1];
}

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