Submission #1118225

#	Time	Username	Problem	Language	Result	Execution time	Memory
1118225		vjudge1	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	17 ms	31824 KiB

kangaroo

// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
 
#include <bits/stdc++.h>
using namespace std;
 
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vi vector<int>
#define vl vector<ll>
#define vii vector<pii>
#define db long double
#define vll vector<pll>
#define endl '\n'
#define all(x) x.begin(), x.end()
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
 
#define int long long

const int sz = 2e3 + 5;
const int mod = 1e9 + 7;
int n, cs, cf, dp[sz][sz];

void fmain(){
    cin >> n >> cs >> cf;
    dp[1][1] = 1;
    for(int i = 2; i <= n; i++){
        for(int j = 1; j <= n; j++){
            if(i == cs or i == cf){
                dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j]) % mod;
                continue;
            }
            dp[i][j] = (dp[i - 1][j - 1] * (j - (i > cs) - (i > cf)) + dp[i - 1][j + 1] * j) % mod;
        }
    }
    cout << dp[n][1];
}
 
signed main(){
    int tmr = 1;
    // cin >> tmr;
    while(tmr--){
        fmain();
    }
    
}

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