PHP Exercises: Test if circumference of two circles intersect or overlap

PHP: Exercise-58 with Solution

There are two circles C1 with radius r1, central coordinate (x1, y1) and C2 with radius r2 and central coordinate (x2, y2)
Write a PHP program to test the followings -
"C2 is in C1" if C2 is in C1
"C1 is in C2" if C1 is in C2
"Circumference of C1 and C2 intersect" if circumference of C1 and C2 intersect, and and "C1 and C2 do not overlap" if C1 and C2 do not overlap.

Input:Input numbers (real numbers) are separated by a space.
Input 0 to exit.

Sample Solution:

PHP Code:

<?php
// Read the number of test cases from standard input
$n = intval(fgets(STDIN));

// Loop through each test case
for ($i = 0; $i < $n; $i++) {
    // Read the coordinates and radii of two circles from standard input
    fscanf(STDIN, "%lf %lf %lf %lf %lf %lf", $xa, $ya, $ra, $xb, $yb, $rb);

    // Calculate the distance between the centers of the two circles
    $r = sqrt(($xb - $xa) * ($xb - $xa) + ($yb - $ya) * ($yb - $ya));

    // Check if one circle is completely inside the other
    if ($r + $ra < $rb) {
        echo "C1 is in C2\n";
        continue;
    }

    if ($r + $rb < $ra) {
        echo "C2 is in C1.\n";
        continue;
    }

    // Check if the circumferences of the circles intersect
    if ($r <= $ra + $rb) {
        echo "Circumference of C1 and C2 intersect.\n";
        continue;
    }

    // Circles do not overlap or intersect
    echo "C1 and C2 do not overlap.\n";
}

?>

Explanation:

• Read Number of Test Cases:
• The first line reads an integer from standard input, which represents the number of test cases ($n).
• Loop Through Each Test Case:
• A for loop iterates from 0 to n-1, processing each test case.
• Read Circle Data:
• For each test case, the coordinates and radii of two circles are read from standard input using fscanf().
• Variables $xa, $ya, $ra represent the center coordinates and radius of Circle 1 (C1).
• Variables $xb, $yb, $rb represent the center coordinates and radius of Circle 2 (C2).
• Calculate Distance Between Centers:
• The distance between the centers of the two circles is calculated using the distance formula: r=(xb−xa)2+(yb−ya)2r = \sqrt{(xb - xa)^2 + (yb - ya)^2}r=(xb−xa)2+(yb−ya)2
• Check If One Circle Is Inside the Other:
• Circle 1 inside Circle 2: If the sum of the radius of Circle 1 and the distance between the centers is less than the radius of Circle 2, it outputs "C1 is in C2".
• Circle 2 inside Circle 1: If the sum of the radius of Circle 2 and the distance is less than the radius of Circle 1, it outputs "C2 is in C1".
• Check If Circles Intersect:
• If the distance between the centers is less than or equal to the sum of the radii of both circles, it outputs "Circumference of C1 and C2 intersect".
• Circles Do Not Overlap:
• If none of the previous conditions are met, it outputs "C1 and C2 do not overlap".

Sample Input:
2
0.0 0.0 6.0 0.0 0.0 5.0
0.0 0.0 3.0 5.1 0.0 3.0

Sample Output:

C2  is in C1.
Circumference of C1  and C2  intersect.

Flowchart:

PHP Code Editor:

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