[T13365]他

原題鏈接

摺疊時
做好對應

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
#include<queue>
#include<vector>
#include<climits>
#include<string>
#include<cstdlib>
#include<ctime>
#define MOD 1000000007
#define LL long long
using namespace std;

LL n,m,l,r,mid[3005],i,j,len;

int main()
{   
    scanf("%lld%lld",&n,&m);

    l=0;
    r=n;

    for(i=1;i<=m;i++)
        scanf("%lld",&mid[i]);

    for(i=1;i<=m;i++)
    {
        for(j=i+1;j<=m;j++)
        {
            if(mid[i]-l>r-mid[i])
            {
                if(mid[j]>mid[i]) mid[j]=2*mid[i]-mid[j];
            }   

            else
            {
                if(mid[j]<mid[i]) mid[j]=2*mid[i]-mid[j];
            }
        }

        if(mid[i]-l>r-mid[i])
        {
            r=mid[i];
            len=mid[i]-l;
        }

        else
        {
            l=mid[i];
            len=r-mid[i];
        }
    }

    printf("%lld",len);

    return 0;
}