Any Way You Slice It （向量旋转 以及 判断线段是否相交）（模板）

http://acm.hunnu.edu.cn/online/?action=problem&type=show&id=11353

 #include<iostream>
 #include<stdio.h>
 #include<string>
 #include<math.h>
 #define PI acos(-1)
 //using namespace std;
 struct Nod
 {
     int dir;
     int len;
 }node[];
 struct Point
 {
 double x;
 double y;
 };
 struct segmemt
 {
     Point s;
     Point t;
 };
 double MAX(double a,double b)
 {
 if(a>b)return a;
 return b;
 }
 double MIN(double a,double b)
 {
 if(a<b)return a;
 return b;
 }
 double mulpti(Point ps , Point pe , Point p)
 {
 return (pe.x-ps.x)*(p.y-ps.y)-(p.x-ps.x)*(pe.y-ps.y);
 }
 bool inser(Point p1, Point p2 , Point p3, Point p4)  //判断线段是否相交
 {
 if(MAX(p1.x,p2.x)>=MIN(p3.x,p4.x) &&
      MAX(p3.x,p4.x)>=MIN(p1.x,p2.x) &&
      MAX(p1.y,p2.y)>=MIN(p3.y,p4.y) &&
      MAX(p3.y,p4.y)>=MIN(p1.y,p2.y) &&
      mulpti(p1,p2,p3)*mulpti(p1,p2,p4)<= &&
      mulpti(p3,p4,p1)*mulpti(p3,p4,p2)<=)
      return true;  //相交
 else
      return false;  //不相交
 }

 //得到向量的x坐标
 double getX(double x,double y,int dir) //传入(x,y)向量以及角度dir
 {
     return x*cos(dir/180.0*PI)-y*sin(dir/180.0*PI);
 }
 //得到向量的y坐标
 double getY(double x,double y,int dir)
 {
     return y*cos(dir/180.0*PI)+x*sin(dir/180.0*PI);
 }

 int main()
 {
     int n;
     segmemt list[];
     while(~scanf("%d",&n)&&n)
     {
         int i;
         double x,y,tx,ty;
         for(i=;i<n;i++)
         {
             scanf("%d%d",&node[i].dir,&node[i].len);
             if(node[i].dir<)   node[i].dir=+node[i].dir;
         }
         list[].s.x=;
         list[].s.y=;
         x = getX(,,node[].dir);
         y = getY(,,node[].dir);
         list[].t.x = x*node[].len;
         list[].t.y = y*node[].len;
         for(i=;i<n;i++)
         {
             list[i].s.x = list[i-].t.x;
             list[i].s.y = list[i-].t.y;
             tx = x;
             ty = y;
             x = getX(tx,ty,node[i].dir);
             y = getY(tx,ty,node[i].dir);
             list[i].t.x = x*node[i].len + list[i].s.x;
             list[i].t.y = y*node[i].len + list[i].s.y;
         }
         int j,flag=;
         for(i=;i<n;i++)
         {
             for(j=;j<=i-;j++)
             {
                 if(inser(list[j].s,list[j].t,list[i].s,list[i].t))
                 {
                     flag = ;
                     printf("%d\n",i+);
                     break;
                 }
             }
             if(flag)    break;
         }
         if(!flag)
         {
             puts("SAFE");
         }
     }
     return ;
 }