poj-3270-Cow Sorting-置换群

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参考：http://lolita-angel.diandian.com/post/2012-10-18/40040595942

寻找一个自我置换群，然后求这个群的最小置换。

#include <stdio.h>#include<string.h>#include<iostream>#include<algorithm>#include<stdlib.h>#include<math.h>#include<stack>#define LL long long#define maxn 20000using namespace std;struct list{    int x;    int y;}node[maxn];int cmp(struct list a,struct list b){    return a.x<b.x;}int a[maxn];int b[maxn];int vis[maxn];int main(){    int i,n,k;    int minn;    while(~scanf("%d",&n))    {        memset(vis,0,sizeof(vis));        minn=9999999;        for(i=1;i<=n;i++)        {            scanf("%d",&a[i]);            minn=min(minn,a[i]);            node[i].x=a[i];            node[i].y=i;        }        sort(node+1,node+n+1,cmp);        for(i=1;i<=n;i++)b[node[i].y]=i;        LL sum=0;        LL sum1,sum2;        int mm;        for(i=1;i<=n;i++)        {            if(vis[i])continue;            if(i==b[i])continue;            sum1=sum2=0;            mm=9999999;            int j=i;            int tt;            tt=0;            while(vis[j]==0)            {                tt++;                vis[j]=1;                sum1+=a[j];                mm=min(mm,a[j]);                sum2+=a[j];                j=b[j];            }            sum1=sum1-mm+(tt-1)*mm;            sum2=mm+minn+sum2+tt*minn;            sum+=min(sum1,sum2);        }        cout<<sum<<endl;    }    return 0;}

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