POJ 2606

#include<iostream>
#include<set>
#include<stdio.h>
#include<math.h>
#include<algorithm>
#define MAXN 705
using namespace std;
int num;
double p[MAXN][2];
double a[MAXN*MAXN];
set<int> coll;
set<int>::iterator pos;
multiset<int> coll_main;
int main()
{
//freopen("acm.acm","r",stdin);
int i;
int max;
int j;
int k;
int t;
double value;
int num;
double s2;
scanf("%d",&num);
max = 0;
for(i = 0; i < num; ++ i)
{
scanf("%lf%lf",&p[i][0],&p[i][1]);
}
for(i = 0; i < num; ++ i)
{
k = 0;
for(j = 0; j < num; ++ j)
{
if(i != j)
{
value = (p[i][0] - p[j][0]) / (p[i][1] - p[j][1]);
a[k] = value;
++ k;
}
}
sort(a,a + k);
s2 = a[0];
j = 0;
for(t = 0; t < k; ++ t)
{
if(a[t] == s2)
++ j;
else
{
if(j > max)
{
max = j;
}
s2 = a[t];
-- t;
j = 0;
}
}
if(j > max)
max = j;
}
++max;
cout<<max<<endl;
}