UVA-10570 Meeting with Aliens （枚举+贪心）

# include<iostream>
# include<cstdio>
# include<cstring>
# include<algorithm>
using namespace std;

int a[2000],head,tail,n,b[505];

bool ok(int id,int d)
{
for(int i=0;i<n;++i){
int p=(id+d*b[i]-d+n)%n;
if(p!=i)
return false;
}
return true;
}

int getAns(int id,int d)
{
for(int i=0;i<n;++i)  b[i]=a[i];
int res=0;
while(!ok(id,d))
{
for(int i=0;i<n;++i){
int p=(id+d*b[i]-d+n)%n;
if(i!=p){
++res;
swap(b[i],b[p]);
}
}
}
return res;
}

void solve()
{
head=0,tail=n;
while(a[head]!=1)
a[tail++]=a[head++];
for(int i=0;i<n;++i)
a[i]=a[head++];

int ans=100000000;
for(int i=0;i<n;++i)
ans=min(ans,min(getAns(i,1),getAns(i,-1)));
printf("%d\n",ans);
}

void read()
{
for(int i=0;i<n;++i)
scanf("%d",a+i);
}

int main()
{

///freopen("UVA-10570 Meeting with Aliens.txt","r",stdin);
while(scanf("%d",&n)&&n)
{
read();
solve();
}
return 0;
}