Submission #1118257

#	Time	Username	Problem	Language	Result	Execution time	Memory
1118257		vjudge1	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	30 ms	23132 KiB

kangaroo

#include <bits/stdc++.h>

// #pragma GCC optimize("Ofast,no-stack-protector,unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
// #define ll long long
#define int long long
#define pii pair<int, int>
#define all(v) v.begin(), v.end()
using namespace std;
const int oo = 1e9 + 9;
const int MAX = 2000 + 5, LOGMAX = 20, B = 441, MOD = 1e9 + 7;

int dp[MAX][MAX];

void solve(){
    int n, cs, cf; cin >> n >> cs >> cf;
    dp[1][1] = 1;
    for(int i = 2; i <= n; i++){
        for(int j = 1; j <= i; j++){
            if(i == cs || i == cf){
                dp[i][j] += dp[i - 1][j];
                dp[i][j] += dp[i - 1][j - 1];
            }
            else{
                dp[i][j] += dp[i - 1][j - 1] * (j - (i > cs) - (i > cf)) % MOD;
                dp[i][j] += dp[i - 1][j + 1] * j % MOD;
            }
            dp[i][j] %= MOD;
        }
    }
    cout << dp[n][1] << '\n';
}

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

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