百练 2624 4th Point .

水题一道..  题目地址：http://www.bailian.openjudge.cn/practice/2624

#include<iostream>#include<cstdio>using namespace std;struct Point{  //点 double x,y;Point(double x,double y):x(x),y(y) {}Point operator + (const Point& p){return Point(x+p.x,y+p.y);}Point operator - (const Point& p){return Point(x-p.x,y-p.y);}bool operator == (const Point& p){return x==p.x&&y==p.y;}};ostream& operator << (ostream &out,const Point& v){printf("%.3lf %.3lf",v.x,v.y);}int main(){double x1,y1,x2,y2,x3,y3,x4,y4;while(scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3,&x4,&y4)!=EOF){Point a(x1,y1),b(x2,y2),c(x3,y3),d(x4,y4);if(a==b) cout<<(c+d-a);else if(a==c) cout<<(b+d-a);else if(a==d) cout<<(c+b-a);else if(b==c) cout<<(a+d-b);else if(b==d) cout<<(a+c-b);else if(c==d) cout<<(a+b-c);cout<<endl;}return 0;}