1. PHP Functions Coding Question
Write a function to calculate the factorial of a number (a non-negative integer). The function accepts the number as an argument.
Case 1: If argument is -3. Output: Invalid input
Case 2: If argument is 5. Output: 5x4x3x2x1=120
Enter a non-negative integer: 5
5x4x3x2x1=120
<?php
/* Enter your code here. Read input from STDIN. Print output to STDOUT */
// Function to calculate the factorial of a number
function factorial($n) {
if ($n < 0) {
return "Invalid Argument";
}
$result = 1;
$factorial_string = "";
for ($i = $n; $i > 0; $i--) {
$result *= $i;
$factorial_string .= "$i" . ($i != 1 ? "x" : "");
}
return "$factorial_string=$result";
}
// Read user input from standard input
// echo "Enter a non-negative integer: ";
$input = trim(fgets(STDIN));
// Convert user input to integer
$n = intval($input);
// Calculate factorial and print output
echo factorial($n);Enter a non-negative integer: 5
5x4x3x2x1=120
Explanation:
The program now modifies the factorial function to also create a string that represents the factorial calculation.
Inside the for loop, the function appends each number and "x" to the string, except for the last number which is appended without "x".
Finally, the function returns the factorial calculation string and the result in the format "factorial calculation=result".
The program then calls the factorial function with the user input as an argument and prints the output to the console.
First read the algorithm, then study the program code line by line. After that, compare the code with the output and finally go through the explanation. This approach helps learners understand both the logic and the implementation properly.
After understanding this example, try to rewrite the same program without looking at the code. Then change some values or logic and run it again. This helps improve confidence and keeps learners engaged on the page for longer.