Submission #362297

#	Time	Username	Problem	Language	Result	Execution time	Memory
362297		Sho10	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	39 ms	23020 KiB

kangaroo

#include <bits/stdc++.h> //Andrei Alexandru a.k.a Sho10
#define ll long long
#define double long double
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define aint(a) (a).begin(), (a).end()
#define f first
#define s second
#define pb push_back
#define mp make_pair
#define pi pair
#define rc(s) return cout<<s,0
#define endl '\n'
#define mod 1000000007
#define PI 3.14159265359
#define INF 1000000005
#define LINF 1000000000000000005ll
#define CODE_START  ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
ll n,s1,s2,dp[2005][2005];
void sum(ll &a, ll b){
    a+=b;
    if(a>=mod)a-=mod;
}
int32_t main(){
CODE_START;
cin>>n>>s1>>s2;
if(s1>s2){
    swap(s1,s2);
}
dp[1][0]=1;
for(ll i=1;i<=n;i++)
{
    for(ll j=0;j<=i;j++)
    {
        if(i!=s1&&i!=s2){
            if(i<n&&j){
                sum(dp[i+1][j-1],1ll*dp[i][j]*j*(j-1)%mod);
            }
            if(i<n&&j<n){
                sum(dp[i+1][j+1],dp[i][j]);
            }
            if(i>s1&&i<n&&j){
                sum(dp[i+1][j-1],1ll*dp[i][j]*j%mod);
            }
            if(i>s2&&i<n&&j){
                sum(dp[i+1][j-1],1ll*dp[i][j]*j%mod);
            }
        }else {
            sum(dp[i+1][j],dp[i][j]);
            if(j){
                sum(dp[i+1][j-1],1ll*dp[i][j]*j%mod);
            }
    }
}
}
cout<<dp[n][0]<<endl;
}

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