Question

Write a C program to find intersection of two lines.

Answer 1

#include <stdio.h>

void main ()

{

   float slope1, intercept_c1, slope2, intercept_c2;

   float x1, y1, x2, y2;

   float intersection ptX, intersection ptY;

   x1=1;

   y1=2;

   x2=5;

   y2=7;

   slope1=(y2-y1)/(x2-x1);

   printf("Slope of line1:%f\n",slope1);

   intercept_c1=y1 - slope1*x1;

   printf("Intercept of line1:%f\n",intercept_c1);

   x1=3;

   y1=3;

   x2=4;

   y2=5;

   slope2=(y2-y1)/(x2-x1);

   printf ("Slope of line2:%f\n",slope2);

   intercept_c2=y1 - slope2*x1;

   printf("Intercept of line2:%f\n",intercept_c2);

   printf("Equation of line1: Y = %.2fX %c %.2f\n", slope1, (intercept_c1 < 0) ? ' ‘: '+',  intercept_c1);

   printf("Equation of line2: Y = %.2fX %c %.2f\n", slope2, (intercept_c2 < 0) ? ' ‘: '+',  intercept_c2);

    if((slope1 - slope2) == 0)

      printf("No Intersection between the lines\n");

   else

   {

       Intersection ptX = (intercept_c2 - intercept_c1) / (slope1 - slope2);

       intersection ptY = slope1 * intersection ptX + intercept_c1;

       printf("Intersecting Point: = %.2f, %.2f\n", intersection ptX, intersection ptY);

   }

}

Explanation:  

The above program finds the intersection of two lines for the given end points of those lines.  

Step 1: Find the slope for first line, using formula slope = (y2 - y1) / (x2 - x1) and also calculate the intercept using formula intercept = y1- slope * x1.

Step 2: Find the slope and intercept for second line using the formula mentioned in step 1.

Step 3: Using the slope and the intercept, intersecting point of the two lines can be calculated as follows:

If the difference between the slope of two lines are ZERO, then there is no intersection.

Else

intersection_ptX = (intercept_c2 - intercept_c1) / (slope1 - slope2);

intersection_ptY = slope1 * intersection_ptX + intercept_c1;