Submission #1127731

#	Time	Username	Problem	Language	Result	Execution time	Memory
1127731		Nelt	Kangaroo (CEOI16_kangaroo)	C++20	6 / 100	0 ms	464 KiB

kangaroo

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define endl "\n"

using namespace std;
using namespace __gnu_pbds;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
template <typename T, typename key = less_equal<T>>
using ordered_set = tree<T, null_type, key, rb_tree_tag, tree_order_statistics_node_update>;
const ll N = 2005, mod = 1e9 + 7;
ll dp[N][N];
void solve()
{
    ll n, cs, cf;
    cin >> n >> cs >> cf;
    dp[1][1] = 1;
    ll cur = 0;
    for (ll i = 2; i <= n; i++)
    {
        if (i == cs or i == cf)
        {
            for (ll j = 1; j < i; j++) dp[i][j] = (dp[i][j] + dp[i - 1][j]) % mod, dp[i][j + 1] = (dp[i][j + 1] + dp[i - 1][j]) % mod;
            cur++;
            continue;
        }
        for (ll j = 1; j < i; j++)
            dp[i][j - 1] = (dp[i][j - 1] + dp[i - 1][j] * (j - 1)) % mod, dp[i][j + 1] = (dp[i][j + 1] + dp[i - 1][j] * (j + 1 - cur)) % mod;
    }
    cout << dp[n][1] << endl;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    ll t = 1;
    // precomp();
    // cin >> t;
    for (ll cs = 1; cs <= t; cs++)
        solve();
    // cerr << "\nTime elapsed: " << clock() * 1000.0 / CLOCKS_PER_SEC << " ms\n";
}

• Subtask 1: 6 / 6
• Subtask 2: 0 / 30
• Subtask 3: 0 / 15
• Subtask 4: 0 / 49