Intersecting Lines---poj1269(求两直线的位置关系)
Posted 西瓜不懂柠檬的酸
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题目链接:http://poj.org/problem?id=1269
题意:给你两条直线上的任意不同的两点,然后求两条直线的位置关系,如果相交于一点输出该点坐标;
#include<iostream> #include<algorithm> #include<math.h> #include<string.h> #include<stdio.h> #include<map> #include<vector> #include<queue> using namespace std; #define met(a, b) memset(a, b, sizeof(a)) #define mod 1000000007 typedef long long LL; ////////////////////////////////////////////////////////////// const int INF = 0x3f3f3f3f; const int N = 21; const double eps = 1e-8; int Sign(double x) { if(fabs(x) < eps) return 0; if(x<0) return -1; return 1; } struct point { double x, y; point(double x_=0, double y_=0):x(x_),y(y_){} point operator -(const point &b)const { return point(x-b.x, y-b.y); } double operator ^(const point &b)const { return (x*b.y - b.x*y); } }; struct line { point p1, p2; line(){} line(point p1_, point p2_):p1(p1_), p2(p2_){} }; ///找到直线L1与L2的交点p0,返回值不同,含义不同; int FindLinePoint(line L1, line L2, point &p0) { double k = ((L1.p1-L1.p2) ^ (L2.p1-L2.p2)); if(Sign(k) == 0) { double t = ((L1.p1-L1.p2)^(L1.p1-L2.p1)); if(Sign(t) == 0) return 2;///共线; return 1;///平行 } p0 = L1.p1; double t = ((L1.p1-L2.p1)^(L2.p1-L2.p2))/((L1.p1-L1.p2)^(L2.p1-L2.p2)); p0.x += (L1.p2.x - L1.p1.x)*t; p0.y += (L1.p2.y - L1.p1.y)*t; return 3;///相交于一点p0; } int main() { printf("INTERSECTING LINES OUTPUT\\n"); int T; scanf("%d", &T); while(T--) { point p0; double x1, y1, x2, y2, x3, y3, x4, y4; scanf("%lf%lf%lf%lf%lf%lf%lf%lf", &x1,&y1, &x2,&y2, &x3,&y3, &x4,&y4); line L1 = line(point(x1,y1), point(x2,y2)); line L2 = line(point(x3,y3), point(x4,y4)); int ans = FindLinePoint(L1, L2, p0); if(ans == 1) printf("NONE\\n");///平行; if(ans == 2) printf("LINE\\n");///共线; if(ans == 3) printf("POINT %.2f %.2f\\n", p0.x, p0.y); } printf("END OF OUTPUT\\n"); return 0; }
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