C++程式:應用上-下-上測試查詢點相對於直線的位置
這是一個C++程式,用於應用上-下-上測試來查詢點相對於直線的位置。對於平面上的任意點t (xt, yt),其相對於連線m和n的直線L的位置可以透過計算標量s來找到 -
Y = A xt + B yt + C
如果Y< 0,則t位於L的順時針半平面;如果Y>0,則t位於逆時針半平面;如果Y= 0,則t位於L上。
演算法
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
示例程式碼
#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;
}輸出
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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