C++程序:应用上-下-上测试查找点相对于直线的位置
这是一个C++程序,用于应用上-下-上测试来查找点相对于直线的位置。对于平面上的任意点t (xt, yt),其相对于连接m和n的直线L的位置可以通过计算标量s来找到 -
Y = A xt + B yt + C
如果Y< 0,则t位于L的顺时针半平面;如果Y>0,则t位于逆时针半平面;如果Y= 0,则t位于L上。
算法
Begin Take the points as input. For generating equation of the line, generate random numbers for coefficient of x and y (x1,x2,y1,y2) by using rand function at every time of compilation. Compute s as (y2 - y1) * x + (x1 - x2) * y + (x2 * y1 - x1 * y2). if (s < 0) Print "The point lies below the line or left side of the line". else if (s >0) print "The point lies above the line or right side of the line"; else print "The point lies on the line" End
示例代码
#include<stdlib.h> #include<iostream> #include<math.h> #include<time.h> using namespace std; const int L = 0; const int H= 20; int main(int argc, char **argv) { time_t seconds; time(&seconds); srand((unsigned int) seconds); int x1, x2, y1, y2; x1 = rand() % (H - L + 1) + L; x2 = rand() % (H - L + 1) + L; y1 = rand() % (H - L + 1) + L; y2 = rand() % (H - L + 1) + L; cout << "The Equation of the 1st line is : (" << (y2 - y1) << ")x+(" << (x1 - x2) << ")y+(" << (x2 * y1 - x1 * y2) << ") = 0\n"; int x, y; cout << "\nEnter the point:"; cin >>x; cin >>y; int s = (y2 - y1) * x + (x1 - x2) * y + (x2 * y1 - x1 * y2); if (s < 0) cout << "The point lies below the line or left side of the line"; else if (s >0) cout << "The point lies above the line or right side of the line"; else cout << "The point lies on the line"; return 0; }
输出
The Equation of the 1st line is : (7)x+(0)y+(-105) = 0 Enter the point:7 6 The point lies below the line or left side of the line
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