POJ 1269 Intersecting Lines 直线交

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>
#include <cstdlib>
#include <cmath>
#include <map>
#include <sstream>
#include <queue>
#include <vector>
#define MAXN 100005
#define MAXM 211111
#define eps 1e-8
#define INF 500000001
using namespace std;
inline int dblcmp(double d)
{
if(fabs(d) < eps) return 0;
return d > eps ? 1 : -1;
}
struct point
{
double x, y;
point(){}
point(double _x, double _y): x(_x), y(_y) {}
void input()
{
scanf("%lf%lf", &x, &y);
}
bool operator ==(point a)const
{
return dblcmp(a.x - x) == 0 && dblcmp(a.y - y) == 0;
}
point sub(point p)
{
return point(x - p.x, y - p.y);
}
double det(point p)
{
return x * p.y - y * p.x;
}

}p[3333];
struct line
{
point a, b;
line(){}
line(point _a, point _b){ a = _a; b = _b;}
void input()
{
a.input();
b.input();
}
int relation(point p)
{
int c = dblcmp(p.sub(a).det(b.sub(a)));
if (c < 0) return 1;
if (c > 0) return 2;
return 3;
}

bool parallel(line v)
{
return dblcmp(b.sub(a).det(v.b.sub(v.a))) == 0;
}

int linecrossline(line v)
{
if ((*this).parallel(v))
{
return v.relation(a) == 3;
}
return 2;
}
point crosspoint(line v)
{
double a1 = v.b.sub(v.a).det(a.sub(v.a));
double a2 = v.b.sub(v.a).det(b.sub(v.a));
return point((a.x * a2 - b.x * a1) / (a2 - a1), (a.y * a2 - b.y * a1) / (a2 - a1));
}

}X, Y;
int n;
int main()
{
puts("INTERSECTING LINES OUTPUT");
scanf("%d", &n);
for(int i = 0; i < n; i++)
{
X.input();
Y.input();
int c = X.linecrossline(Y);
if(c == 0) puts("NONE");
else if(c == 1) puts("LINE");
else
{
point a = X.crosspoint(Y);
printf("POINT %.2f %.2f\n", a.x, a.y);
}
}
puts("END OF OUTPUT");
return 0;
}