UVA 11800 Determine the Shape

题目链接：https://vjudge.net/problem/UVA-11800

题意：给n个四边形，判断是正方形，矩形，菱形，平行四边形，梯形还是普通四边形

水题，随便写，只要知道各个形状的规律就可以了

#include<iostream>#include<cstdio>#include<algorithm>#include<cstring>#include<string>#include<stack>#include<queue>#include<deque>#include<set>#include<map>#include<cmath>#include<vector>using namespace std;typedef long long ll;typedef unsigned long long ull;typedef pair<int, int> PII;#define pi acos(-1.0)#define eps 1e-10#define pf printf#define sf scanf#define lson rt<<1,l,m#define rson rt<<1|1,m+1,r#define e tree[rt]#define _s second#define _f first#define all(x) (x).begin,(x).end#define mem(i,a) memset(i,a,sizeof i)#define for0(i,a) for(int (i)=0;(i)<(a);(i)++)#define for1(i,a) for(int (i)=1;(i)<=(a);(i)++)#define mi ((l+r)>>1)#define sqr(x) ((x)*(x))struct Point{    int x,y;    Point(){}    Point(int x,int y):x(x),y(y){}    Point operator -(const Point& b)    {        return Point(x-b.x,y-b.y);    }}a[5],p;bool cmp(const Point& a,const Point& b){    if(a.x!=b.x)        return a.x<b.x;    return a.y<b.y;}int cal(Point a,Point b)//判断两个向量是否垂直{    return a.x*b.x+a.y*b.y;}double len(Point a,Point b)//计算长度是否相等{    return sqrt(pow(a.x-b.x,2)+pow(a.y-b.y,2));}bool px(Point a,Point b,Point c,Point d)//叉乘计算是否平行{    return (a.x-b.x)*(c.y-d.y)==(a.y-b.y)*(c.x-d.x);}const int inf=0x3f3f3f3f;int t;int main(){    sf("%d",&t);    for1(i,t)    {        for1(i,4)            sf("%d%d",&a[i].x,&a[i].y);        sort(a+1,a+5,cmp);//将四个点按照横坐标小的在前面，相同的话纵坐标小的在前面的        double p=len(a[1],a[2]);        double b=len(a[1],a[3]);        int c=cal(a[1]-a[2],a[1]-a[3]);        int f=cal(a[1]-a[4],a[2]-a[3]);        bool d=px(a[1],a[2],a[3],a[4]);        bool es=px(a[1],a[3],a[2],a[4]);        bool q=px(a[1],a[4],a[2],a[3]);        pf("Case %d: ",i);        if(p==b&&!c&&d&&es)puts("Square");        else if(!c&&d&&es)puts("Rectangle");        else if(d&&es&&!f)puts("Rhombus");        else if(d&&es)puts("Parallelogram");        else if(d||es||q)puts("Trapezium");        else puts("Ordinary Quadrilateral");    }    return 0;}