Submission #1109379

#	Time	Username	Problem	Language	Result	Execution time	Memory
1109379		ASN49K	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	21 ms	14160 KiB

kangaroo

//le privesc ca fiind orientate
#include <bits/stdc++.h>
#include <sys/time.h>
using namespace std;
using i64=long long;
#define UNUSED -1
#define all(x) x.begin(),x.end()
#define pb push_back
const int mod=1e9+7,inf=1e9+1;
const i64 INF=1e18;
int add(int x,int y)
{
    return (x+y)%mod;
}
void add_self(int& x,int y)
{
    x+=y;
    if(x>=mod)
    {
        x-=mod;
    }
}
int prod(int x,int y)
{
    return (1LL*x*y)%mod;
}
mt19937 rng(69);

const int N=2000;
int dp[N][N+2];

int signatura(int x)
{
    if(x>=0)
    {
        return 1;
    }
    return 0;
}
int main()
{
    int n,start,finish;
    cin>>n>>start>>finish;
    start--;
    finish--;
    dp[0][1]=1;
    for(int i=1;i<n;i++)
    {
        for(int j=1;j<=i+1;j++)
        {
            if(i==start || i==finish)
            {
                //adaug ca componenta noua
                add_self(dp[i][j],dp[i-1][j-1]);
                //leg cu cv
                add_self(dp[i][j],dp[i-1][j]);
            }
            else
            {
                //leg 2
                add_self(dp[i][j],prod(dp[i-1][j+1] , j));
                //adaug una noua
                add_self(dp[i][j],prod(dp[i-1][j-1] , j-(i>start)-(i>finish)));
            }
        }
    }
    cout<<dp[n-1][1];
}

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