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;
}