HDU 2013 ACM/ICPC Asia Regional Hangzhou Online ------ Zhuge Liang's Mines

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
struct node
{
int x,y;
}s[50];
int N,ans,v[50];
int cmp(const void *a,const void *b)
{
struct node *c=(struct node *)a;
struct node *d=(struct node *)b;
if(c->y==d->y)
return c->x>d->x;
else return c->y>d->y;
}
void dfs(int num,int sum)/*num记录点的位置，sum记录总共可以移动的地雷数量*/
{
int i,j,cut,n1,n2;
if(ans<sum)ans=sum;
for(i=num;i<N;i++)
{
if(v[i])continue;
v[i]=1;
for(j=i+1;j<N;j++)
{
if(v[j]||s[i].x!=s[j].x||s[i].y==s[j].y)
continue;
v[j]=1;
cut=abs(s[j].y-s[i].y);
for (n1=0;n1<N;n1++)
if (s[n1].x==s[i].x+cut && s[n1].y==s[i].y && !v[n1]) break;//找到对应的那个是否存在
if (n1==N)
{
v[j]=0;
continue;
}
v[n1]=1;
for (n2=0;n2<N;n2++)
if (s[n2].x==s[j].x+cut && s[n2].y==s[j].y && !v[n2]) break;
if (n2==N)
{
v[j]=v[n1]=0;
continue;
}
v[n2]=1;
dfs(i+1,sum+4);
v[j]=v[n1]=v[n2]=0;
}
v[i]=0;
}
}
int main()
{
int i,j;
struct node temp;
while(scanf("%d",&N),N!=-1)
{
for(i=0;i<N;i++)
v[i]=0;
for(i=0;i<N;i++)
scanf("%d%d",&s[i].x,&s[i].y);
/*qsort(s,N,sizeof(s[0]),cmp);*/
/*for(i=0;i<N-1;i++)
{
for(j=i;j<N-1;j++)
if(s[j].y>s[j+1].y)
temp=s[j],s[j]=s[j+1],s[j+1]=temp;
else if(s[j].y==s[j+1].y&&s[j].x>s[j+1].x)
temp=s[j],s[j]=s[j+1],s[j+1]=temp;
}*/
/*for(i=0;i<N;i++)
printf("(%d,%d)\n",s[i].x,s[i].y);*/
ans=0;
dfs(0,0);
printf("%d\n",ans);
}
return 0;
}