UVA 1382 - Distant Galaxy

#include <cstdio>
#include <algorithm>
using namespace std;
struct Point
{
int x,y;
bool operator < (const Point& a) const{
return x<a.x;
}
};
const int maxn=100+5;
Point p[maxn];
int n,m,y[maxn],on[maxn],on2[maxn],left[maxn];
int solve(){
sort(p,p+n);
sort(y,y+n);
m=unique(y,y+n)-y;
if(m<=2) return n;
int ans=0;
for(int a=0;a<m;a++){
for(int b=a+1;b<m;b++){
int ymin=y[a],ymax=y[b];
int k=0;
for(int i=0;i<n;i++){
if(i==0 || p[i].x !=p[i-1].x){
k++;
on[k]=on2[k]=0;
left[k]=k==0?0:left[k-1]+on2[k-1]-on[k-1];
}
if(p[i].y>ymin && p[i].y<ymax) on[k]++;
if(p[i].y>=ymin && p[i].y<=ymax) on2[k]++;
}
if(k<=2) return n;
int M=0;
for(int j=1;j<=k;j++){
ans=max(ans,left[j]+on2[j]+M);
M=max(M,on[j]-left[j]);
}
}
}
return ans;
}
int main(){
int kase=0;
while(scanf("%d",&n)==1 && n){
for(int i=0;i<n;i++){
scanf("%d%d",&p[i].x,&p[i].y);
y[i]=p[i].y;
}
printf("Case %d: %d\n",++kase,solve());
}
return 0;
}