HDU-2007 Scrambled Polygon 极角排序

题目地址

题意：就是将所给点按凸包顺序输出，从原点开始。

分析：其实就是将除原点外的点进行极角排序。

#include<stdio.h>#include<algorithm>#include<math.h>using namespace std;const int maxn = 55;int n,r;struct Point{double x,y;Point( double x = 0,double y = 0 ): x(x),y(y) { }}point[maxn],ch[maxn];double Cross( Point A,Point B,Point C ){    return ( A.x - C.x ) * ( B.y - C.y ) - ( B.x - C.x ) * ( A.y - C.y );}bool cmp( Point A,Point B ){    return Cross( A,B,point[0] ) >= 0;}int main(){    n = 0;while( scanf("%lf%lf",&point[n].x,&point[n].y) != EOF ){ n ++; }    sort( point+1,point+n,cmp );    for( int i = 0; i < n; i ++ )        printf("(%.0lf,%.0lf)\n",point[i].x,point[i].y);return 0;}