pku3668 Game of Lines

http://poj.org/problem?id=3668

水题，STL

#include <stdio.h>
#include <set>

using namespace std;

set<pair<int, int> > set1;

int gcd(int x, int y)
{
    return y? gcd(y, x%y): x;
}

int abs(int x)
{
    return x<0? -1*x: x;
}

struct P
{
    int x, y;
}p[1234];

int main()
{
    int n, i, j;
    int x, y, gcd_xy;
    while(~scanf("%d", &n))
    {
        set1.clear();
        for(i=1; i<=n; i++)
        {
            scanf("%d%d", &p[i].x, &p[i].y);
        }
        for(i=1; i<=n-1; i++)
        {
            for(j=i+1; j<=n; j++)
            {
                x = p[i].x - p[j].x;
                y = p[i].y - p[j].y;
                if(x < 0)
                {
                    x *= -1;
                    y *= -1;
                }
                gcd_xy = gcd(abs(x), abs(y));
                x /= gcd_xy;
                y /= gcd_xy;
                if(x == 0)
                {
                    y = 1;
                }
                if(y == 0)
                {
                    x = 1;
                }
                //printf("%d %d : %d %d\n", i, j, x, y);
                set1.insert(make_pair(x, y));
            }
        }
        printf("%d\n", (int)set1.size());
    }
    return 0;
}