uva 378 Intersecting Lines

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题目：给了4个点，求两条线，判断两条线平行，同一条线，相交（给出交点）

反思：1 功能一块块的写，边写边测，更容易一次性AC

2 网上代码多是用 struct point 来定义坐标，下次可以试试

#include <cstdio>#include <string.h>#include <cstdlib>#include <cmath>#include <ctgmath>#include <iostream>#include <vector>#include <algorithm>#include <map>using namespace std;//由两个点的坐标，求出所在直线方程，返回y=kx+b中的k、bvoid func(double x1,double y1,double x2,double y2,double &k,double &b){    k = (y2-y1)/(x2-x1);    b = y1 - (k*x1);}int main(){    //double x1,y1,x2,y2,k,b;    int num;    cin>>num;    cout<<"INTERSECTING LINES OUTPUT"<<endl;    while (num--) {        double x1,y1,x2,y2,x3,y3,x4,y4;        cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4;                //首先处理不垂直x轴的        if((x1!=x2) && (x3!=x4)){            double k1,b1,k2,b2;            func(x1, y1, x2, y2, k1, b1);            func(x3, y3, x4, y4, k2, b2);            //平行            if(k1==k2 && b1!=b2) cout<<"NONE"<<endl;            //一条线            else if(k1==k2 && b1==b2) cout<<"LINE"<<endl;            //相交            else {                double x,y;                x=(b2-b1)/(k1-k2);                y=k1*x + b1;                printf("POINT %.2lf %.2lf\n",x,y);            }        }        //处理垂直x轴的        else{            if (x1==x2 && x4==x3 && x1==x3) cout<<"LINE"<<endl;            else if(x1==x2 && x4==x3 && x1!=x3) cout<<"NONE"<<endl;            else{                if(x1==x2){                    double k,b;                    func(x3, y3, x4, y4, k, b);                    double x = x1;                    double y = k*x+b;                    printf("POINT %.2lf %.2lf\n",x,y);                }                else{                    double k,b;                    func(x1, y1, x2, y2, k, b);                    double x = x3;                    double y = k*x+b;                    printf("POINT %.2lf %.2lf\n",x,y);                }            }        }    }        cout<<"END OF OUTPUT"<<endl;    return 0;}

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