Submission #580604

#	Time	Username	Problem	Language	Result	Execution time	Memory
580604		vovamr	Kangaroo (CEOI16_kangaroo)	C++17	0 / 100	1 ms	212 KiB

kangaroo

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define fi first
#define se second
#define ll long long
#define ld long double
#define sz(x) ((int)(x).size())
#define all(x) 	(x).begin(), (x).end()
#define pb push_back
#define mpp make_pair
#define ve vector
using namespace std;
using namespace __gnu_pbds;
template<class T> using oset = tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
const ll inf = 1e18; const int iinf = 1e9;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
template <typename T> inline bool chmin(T& a, T b) { return (a > b ? a = b, 1 : 0); }
template <typename T> inline bool chmax(T& a, T b) { return (a < b ? a = b, 1 : 0); }

const int md = 1e9 + 7;
inline int add(int a, int b) { a += b; if (a >= md){a -= md;} return a; }
inline int mul(int a, int b) { return (ll)a * b % md; }

inline void solve() {
	int n, s, t;
	cin >> n >> s >> t;
	ve<ve<int>> dp(n + 5, ve<int> (n + 5));

	dp[1][1] = 1;
	for (int i = 1; i < n; ++i) {
		for (int j = 1; j <= i; ++j) {
			if (i + 1 == s || i + 1 == t) {
				dp[i + 1][j] = add(dp[i + 1][j], dp[i][j]);
				dp[i + 1][j + 1] = add(dp[i + 1][j + 1], dp[i][j]);
			}
			else {
				int ways = j + 1 - (i + 1 > s) - (i + 1 > t);
				dp[i + 1][j + 1] = add(dp[i + 1][j + 1], mul(ways, dp[i][j]));

				dp[i + 1][j - 1] = add(dp[i + 1][j], mul(dp[i][j], j - 1));
			}
		}
	}

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

signed main() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	int q = 1; // cin >> q;
	while (q--) solve();
	cerr << fixed << setprecision(3) << "Time execution: " << (double)clock() / CLOCKS_PER_SEC << endl;
}

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