poj1118

简单题

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

#define maxn 705
#define eps 10E-9

struct Point
{
    int x, y;
} point[maxn];

struct Node
{
    double k;
    int a, b;
} f[maxn * maxn];

int n, ncount;
double inf;

bool operator <(const Point &a, const Point &b)
{
    return (a.x == b.x && a.y < b.y) || a.x < b.x;
}

bool operator <(const Node &a, const Node &b)
{
    if (abs(a.k - b.k) > eps)
        return a.k < b.k;
    return (a.a == b.a && a.b < b.b) || a.a < b.a;
}

double cal(Point &a, Point &b)
{
    if (a.x == b.x)
        return inf;
    return (b.y - a.y) * 1.0 / (b.x - a.x);
}

int main()
{
    inf = 1.79769e+308;
    //freopen("t.txt", "r", stdin);
    while (scanf("%d", &n), n)
    {
        for (int i = 0; i < n; i++)
            scanf("%d%d", &point[i].x, &point[i].y);
        sort(point, point + n);
        ncount = 0;
        for (int i = 0; i < n; i++)
            for (int j = i + 1; j < n; j++)
            {
                f[ncount].a = i;
                f[ncount].b = j;
                f[ncount].k = cal(point[i], point[j]);
                ncount++;
            }
        sort(f, f + ncount);
        int len = 1;
        int ans = 0;
        for (int i = 1; i < ncount; i++)
        {
            if (f[i].a == f[i - len].a && abs(f[i].k - f[i - len].k) < eps)
                len++;
            else
            {
                ans = max(ans, len);
                len = 1;
            }
        }
        printf("%d\n", ans + 1);
    }
    return 0;
}