[恢]hdu 1785

2011-12-21 09:46:27

地址：http://acm.hdu.edu.cn/showproblem.php?pid=1785

题意：中文。给点和原点连线与x轴夹角排序。

代码：

# include <stdio.h>
# include <stdlib.h>


typedef struct point{
    double x, y ;
}point ;


point pt[110] ;


int cmp(const void *a, const void *b)
{
    double x1 = ((point*)a)->x, y1 = ((point*)a)->y ;
    double x2 = ((point*)b)->x, y2 = ((point*)b)->y ;
    double diff = x2*y1 - x1*y2 ;
    if (diff < 1e-9 && diff >-1e-9) return 0 ;
    else if (diff < 0) return -1 ;
    else return 1 ;
}


int main ()
{
    int flag, n, i ;
    while (~scanf ("%d", &n) && n >= 0)
    {
        for (i = 0 ; i < n ; i++)
            scanf ("%lf%lf", &pt[i].x, &pt[i].y) ;
        qsort(pt, n, sizeof(point), cmp) ;
        flag = 0 ;
        for (i = 0 ; i < n ; i++)
        {
            if (flag == 0) flag =1  ;
            else printf (" ") ;
            printf ("%.1lf %.1lf", pt[i].x, pt[i].y) ;
        }
        printf ("\n") ;
    }
    return 0 ;
}