PHP Exercises: Restore the original string by entering the compressed string with this rule

Last update on April 19 2025 11:50:25 (UTC/GMT +8 hours)

72. Compressed String Restoration

When character are consecutive in a string , it is possible to shorten the character string by replacing the character with a certain rule. For example, in the case of the character string YYYYY, if it is expressed as # 5 Y, it is compressed by one character.
Write a PHP program to restore the original string by entering the compressed string with this rule. However, the # character does not appear in the restored character string.
Note: The original sentences are uppercase letters, lowercase letters, numbers, symbols, less than 100 letters, and consecutive letters are not more than 9 letters.

Input: Multiple character strings are given. One string is given per line

Sample Solution:

PHP Code:

<?php
// Input string containing "@" symbols with repetition information
$str = "@88 + 1 = 1@80";

// Initialize index for traversing the input string
$index = 0;

// Initialize an array to store the resulting characters
$result = array();

// Loop through each character in the input string
while ($index < strlen($str)) {
    // Get the current character
    $t = $str[$index++];

    // Check if the current character is "@"
    if ($t == "@") {
        // Extract the length and character information for repetition
        $len = $str[$index++];
        $char = $str[$index++];

        // Initialize an empty string to store repeated characters
        $run = "";

        // Repeat the character for the specified length
        for ($i = 0; $i < $len; $i++) {
            $run .= $char;
        }

        // Add the repeated characters to the result array
        $result[] = $run;
    } else {
        // If the character is not "@", add it directly to the result array
        $result[] = $t;
    }
}

// Output the final result by concatenating the characters in the result array
echo implode("", $result);
?>

Explanation:

Initialize Input and Variables:

Defines the input string $str = "@88 + 1 = 1@80", which contains the "@" symbol to denote sections with repetition information.
Initializes $index = 0 to traverse the string and $result = array() to store processed characters.

Loop Through Each Character in $str:

Uses a while loop to go through the string character by character until $index reaches the end.

Check for "@" Symbol:

If the character at $index is "@", it indicates the start of a repetition pattern.
Extract Repetition Information:

Reads the next two characters after "@":

$len: Specifies the number of times to repeat the following character.
$char: The character to be repeated.

Create Repeated String:

Uses a for loop to create a string ($run) with $char repeated $len times and adds it to $result.

Handle Non-"@" Characters:

If the character is not "@", it’s added directly to $result.

Output the Result:

Combines all elements in $result into a single string and displays it using echo implode("", $result);.

Sample Input:
@88 + 1 = 1@80

Sample Output:

88888888 + 1 = 100000000

Flowchart:

For more Practice: Solve these Related Problems:

Write a PHP script to expand a compressed string where a number preceded by '#' represents repeated characters.
Write a PHP script to parse compressed tokens in a string and restore the original text using pattern matching.
Write a PHP script to decompress a string containing multiple compressed segments separated by spaces.
Write a PHP script to validate and restore an input string that uses a custom compression format with '#' symbols.

PHP Code Editor:

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