牛排序——置换群pku3270

hash+置换群

#include<stdio.h>
#include<string.h>
int a[10009];
int hash[100009];
bool use[100009];

int min1(int a,int b)
{
    if(a>b)return b;
    else
        return a;
}

int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        int i,min=9999999,max=0;
        memset(hash,0,sizeof(hash));
        memset(use,0,sizeof(use));

        for(i=1;i<=n;i++)
        {
            scanf("%d",&a[i]);
            if(a[i]<min)min=a[i];
            if(max<a[i])max=a[i];
            hash[a[i]]=1;
            use[a[i]]=1;
        }

        int add=1;//放入hash
        for(i=1;i<=max;i++)
        {
            if(hash[i]==1)
            {
                hash[i]=a[add];
                add++;
            }
        }

        int all=0,j;
        int sum1,sum2,sum,tmin;
        for(i=1;i<=max;i++)
        {
            if(hash[i]==i||use[i]==0)continue;

            j=i;
            sum1=0,sum2=0,sum=0,tmin=j;
            use[j]=0;
            add=1;
            sum+=j;
            while(use[hash[j]]==1)
            {
                j=hash[j];
                use[j]=0;
                if(tmin>j)tmin=j;
                sum+=j;
                add++;
            }
            sum1=sum+(add-2)*tmin;
            sum2=sum+tmin+(add+1)*min;
            all+=min1(sum1,sum2);
        }

        printf("%d\n",all);

    }
}