PHP Exercises: Find the first non-repeated character in a given string

Last update on May 26 2025 13:17:22 (UTC/GMT +8 hours)

42. First Non-Repeated Character

Write a PHP program to find the first non-repeated character in a given string.

Sample Example:

Input: Green
Output: G
Input: abcdea
Output: b

Sample Solution:

PHP Code:

<?php
// Define a function to find the first non-repeating character in a word
function find_non_repeat($word) {
    $chr = null;

    // Iterate through each character in the word
    for ($i = 0; $i <= strlen($word); $i++) {
        // Check if the count of the current character is 1 (non-repeating)
        if (substr_count($word, substr($word, $i, 1)) == 1) {
            // Return the first non-repeating character found
            return substr($word, $i, 1);
        }
    }
}

// Test the function with different words
echo find_non_repeat("Green")."\n";    // Output: G
echo find_non_repeat("abcdea")."\n";   // Output: b

?>

Explanation:

Define Function find_non_repeat($word):

This function finds and returns the first non-repeating character in a given string $word.

Initialize Variable:

$chr is defined but not used (possibly intended to store the result, though it's unnecessary here).

Loop Through Each Character:

for ($i = 0; $i <= strlen($word); $i++) iterates over each character in $word.

Check for Non-Repeating Character:

substr_count($word, substr($word, $i, 1)) == 1 checks if the current character appears only once in the string.

Return First Non-Repeating Character:

If a non-repeating character is found, return substr($word, $i, 1) immediately returns it, ending the function.

Test Cases:

find_non_repeat("Green") outputs "G", as it's the first unique character.
find_non_repeat("abcdea") outputs "b", the first non-repeating character in this word.

Output:

G                                                           
b

Flowchart:

For more Practice: Solve these Related Problems:

Write a PHP function to find the first non-repeated character in a string using associative arrays.
Write a PHP script that scans a string with repeated characters and returns the first unique character.
Write a PHP script to determine the first non-repeating character in a multi-byte Unicode string.
Write a PHP script to optimize the search for the first unique character in very long strings.

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