B - Scrambled Polygon POJ - 极角排序

• B - Scrambled Polygon

•  POJ - 2007 
• 按照与第一个点的夹角排序即可，

• #include<cstdio>
  #include<cmath>
  #include<algorithm>
  using namespace std;
  #define maxn 105
  #define PR 1e-6
  struct node
  {
      int x,y;
  } p[maxn];
  double l,ans;
  int n,stk[maxn],top;
  double cha(node p0,node p1,node p2)
  {
      return (p1.x-p0.x)*(p2.y-p0.y)-(p1.y-p0.y)*(p2.x-p0.x);
  }
  bool cmp(node a,node b)
  {
      return ((cha(p[1],a,b)))>0;
  }
  int main()
  {
      n=1;
      while(~scanf("%d%d",&p[n].x,&p[n].y))
          n++;
      sort(p+2,p+n,cmp);
      int i;
      for(i = 1; i <n; i ++)
          printf("(%d,%d)\n",(p[i].x),(p[i].y));
      return 0;
  }