Submission #1294271

#	Time	Username	Problem	Language	Result	Execution time	Memory
1294271		ezim1234	Kangaroo (CEOI16_kangaroo)	C++20	0 / 100	2 ms	568 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;

#define all(v) v.begin(), v.end()
#define yes cout << "Yes" << "\n"
#define no cout << "No" << "\n"
#define pb push_back
#define F first
#define S second
#define int long long
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
typedef pair <ll, ll> pii;
typedef vector <pii> vii;
typedef vector <ll> vi;
template<typename T>
void read(vector<T>& v) {
    for (auto &x : v) cin >> x;
}

template<typename T>
void print(const vector<T>& v) {
    for (auto &x : v) cout << x << ' ';
    cout << "\n";
}

const ll MAX = 2000 + 5;
const ll MOD = 1e9 + 7;
int dp[MAX][MAX];
int dp1[MAX][MAX];
void solve() {
    int n, s, f;
    cin >> n >> s >> f;
    for (int i = 1; i <= n; i++) {
        if (i == 1) {
            dp[i][s] = 1;
            dp1[i][s] = 1;
            continue;
        }
        int cem = 0;
        int say = 0;
        for (int j = 1; j <= n; j++) {
            if (j != s && (j != f || i == n)) {
                dp[i][j] = (cem + MOD - dp[i - 2][j] * say % MOD) % MOD;
                dp[i][j] = dp[i][j] % MOD;
            }
            cem += dp1[i - 1][j] % MOD;
            cem = cem % MOD;
            if (dp1[i - 1][j] > 0) {
                say++;
            }
        }
        cem = 0;
        say = 0;
        for (int j = n; j >= 1; j--) {
            if (j != s && (j != f || i == n)) {
                dp1[i][j] = (cem + MOD - (dp1[i - 2][j] * say) % MOD) % MOD;
                dp1[i][j] = dp1[i][j] % MOD;
            }
            cem += dp[i - 1][j] % MOD;
            cem = cem % MOD;
            if (dp[i - 1][j] > 0) {
                say++;
            }
        }
    }
    cout << dp1[n][f] + dp[n][f] << '\n';
}
signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int t = 1;
    //cin >> t;
    for (int i = 1; i <= t; i++) {
        solve();
    }
}

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