Submission #1118255

#	Time	Username	Problem	Language	Result	Execution time	Memory
1118255		vjudge1	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	32 ms	23132 KiB

kangaroo

#include<bits/stdc++.h>

#define ll long long
#define pb push_back
#define in insert
#define fi first
#define se second
#define vl vector<ll>
#define all(v) v.begin(), v.end()
#define endl "\n"

using namespace std;
const int sz = 2005; /// mind this $$
const int MAX = 2e6 + 123;
const int BS = 61;
const ll inf = 1e17;
const int mod = 1e9 + 7;
ll dp[sz][sz];
void solve(){
    ll n, st, ed, i, j;
    cin >> n >> st >> ed;
    dp[1][1] = 1;
    for(i = 2; i <= n; i++){
        for(j = 1; j <= i; j++){
            if(i == st || i == ed){
                dp[i][j] = (dp[i][j] + dp[i - 1][j - 1]) % mod;
                dp[i][j] = (dp[i][j] + dp[i - 1][j]) % mod;
            }
            else{
                dp[i][j] = (dp[i][j] + (dp[i - 1][j - 1] * (j - (i > st) - (i > ed))) % mod) % mod;
                dp[i][j] = (dp[i][j] + (dp[i - 1][j + 1] * j) % mod) % mod;

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

}
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    ll t = 1;
    // cin >> t;
    while(t--){
        solve();
    }
}

/*

*/

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