C ++程序检查给定的三点集是否位于单行上
这是一个C++程序，用于检查给定的三个点是否位于同一行上。如果由三点组成的三角形的面积等于零，则该点位于一条直线上。
三角形的面积是-
0.5 * (x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2)).
演算法
Begin
Generate the points randomly.
Calculate the area by using above formula.
If area > 0
Then the points don't lie on the straight line.
else if area < 0
Then the points don't lie on the straight line.
else
The points lie on the straight line.
End示例
#include <iostream>
#include <time.h>
#include <stdlib.h>
using namespace std;
static int L = 1;
static int U= 20;
int main(int argc, char **argv) {
int x3, y3, x1, x2, y1, y2;
time_t seconds;
time(&seconds);
srand((unsigned int) seconds);
//Generate the points randomly using rand().
x1 = rand() % ( U- L+ 1) + L;
y1 = rand() % (U - L+ 1) + L;
x2 = rand() % (U - L + 1) + L;
y2 = rand() % (U - L+ 1) + L;
x3 = rand() % (U - L+ 1) + L;
y3 = rand() % (U - L+ 1) + L;
cout << "The points are: (" << x1 << ", " << y1 << "), (" << x2 << ", " << y2 << "), & (" << x3 << ", " << y3 << ")\n";
//计算面积
float a = 0.5 *(x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2));
if (a < 0)
cout << "The points don't lie on the straight line";
else if (a > 0)
cout << "The points don't lie on the straight line ";
else
cout << "The points lie on the straight line";
}输出结果
The points are: (20, 9), (6, 13), & (13, 11) The points lie on the straight line The points are: (9, 15), (4, 15), & (11, 16) The points don't lie on the straight line