poj 1940 Polygon Programming ...

poj 1940 Polygon Programming ...

#include <iostream>#include <cstdlib>#include <cstdio>#include <cstring>#include <algorithm>#include <cmath>#define N 1010using namespace std;//奇数条边的时候满足，偶数时不确定 struct PO{    double x,y;}s[N],t[N];int n;inline void read(){    for(int i=1;i<=n;i++) scanf("%lf%lf",&s[i].x,&s[i].y);}inline void go(){    double a=0.0,b=0.0;    for(int i=n;i>=1;i--)    {        if(i&1) a+=s[i].x,b+=s[i].y;        else a-=s[i].x,b-=s[i].y;    }    t[1].x=a; t[1].y=b;    for(int i=2;i<=n;i++)    {        t[i].x=t[i-1].x+2.0*(s[i-1].x-t[i-1].x);        t[i].y=t[i-1].y+2.0*(s[i-1].y-t[i-1].y);    }    printf("%d",n);    for(int i=1;i<=n;i++)        printf(" %.6lf %.6lf",t[i].x,t[i].y);    puts("");}int main(){    while(scanf("%d",&n)!=EOF) read(),go();    return 0;}