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Program to check if three points are collinear in C++
Given with three different valued points and the task is to check whether the points are collinear or not.
Points are said to be collinear if they lie on the same line and they are not collinear if they are on the different lines. Given below is the figure of collinear and non-collinear points.
Input
x1 = 1, x2 = 2, x3 = 3, y1 = 1, y2 = 4, y3 = 5
Output
no points are not collinear
Input
x1 = 1, y1 = 1, x2 = 1, y2 = 4, x3 = 1, y3 = 5
Output
points are collinear
Approach used in the below program is as follow
Input the points as (x1, y1), (x2, y2), (x3, y3)
Apply the formula of area of triangle x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2)
check for the conditions as −
if the area of triangle is 0 than print points are collinear
if the area of triangle is not 0 than print points are not collinear
print the final result
Algorithm
Start Step 1→ declare function to check if points are collinear or not void check_collinear(int x1, int y1, int x2, int y2, int x3, int y3) declare int a = x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2) IF (a == 0) Print "yes points are collinear" End Else Print "no points are not collinear" Step 2→ In main() Declare int x1 = 1, x2 = 2, x3 = 3, y1 = 1, y2 = 4, y3 = 5 Call check_collinear(x1, y1, x2, y2, x3, y3) Stop
Example
#include <bits/stdc++.h>
#include <math.h>
#include <stdlib.h>
using namespace std;
//check if points are collinear or not
void check_collinear(int x1, int y1, int x2, int y2, int x3, int y3){
int a = x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2);
if (a == 0)
cout << "yes points are collinear";
else
cout << "no points are not collinear";
}
int main(){
int x1 = 1, x2 = 2, x3 = 3, y1 = 1, y2 = 4, y3 = 5;
check_collinear(x1, y1, x2, y2, x3, y3);
return 0;
}Output
If run the above code it will generate the following output −
no points are not collinear
Updated on: 13-Aug-2020
2K+ Views
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