Linear Search

# Linear Search

Zerethon Official Sample `linear-search`, version 1.1.0, PHP 8.4.

- `linear_search.php` — the algorithm, as shown in Zerethon Tools
- `main.php` — entry file: a short demonstration
- `test_linear_search.php` — checks; set it as the entry file to run them

This project is your own copy. Changing it never changes the official sample.
See the algorithm animated: https://tools.zerethon.com/linear-search-visualizer

<?php

// Linear Search (Zerethon Official Sample: linear-search 1.1.0).
// The algorithm as shown in Zerethon Tools.

// Returns the index of target, or -1. Works on any (unsorted) array.
function linear_search(array $a, int $target): int {
    foreach ($a as $i => $v) {
        if ($v === $target) return $i;
    }
    return -1;
}

<?php

require __DIR__ . '/linear_search.php';

$numbers = [38, 27, 43, 3, 9, 82, 10, 27];
echo 'List: [' . implode(', ', $numbers) . "]\n";
foreach ([43, 27, 38, 5] as $target) {
    $index = linear_search($numbers, $target);
    $result = $index !== -1 ? "found at index {$index}" : 'not found';
    printf("search %2d: %s\n", $target, $result);
}

<?php

// Checks for linear_search. To run them, set this file as the entry file
// (the ▶ button next to it in Files) and press Run.

require __DIR__ . '/linear_search.php';

$cases = [
    [[], 1, -1],
    [[4], 4, 0],
    [[4], 5, -1],
    [[9, 3, 7], 9, 0],
    [[9, 3, 7], 7, 2],
    [[5, 1, 5, 1], 1, 1], // the first match wins
    [range(100, 1), 1, 99],
];

foreach ($cases as [$a, $target, $expected]) {
    $got = linear_search($a, $target);
    if ($got !== $expected) {
        fwrite(STDERR, "linear_search(..., {$target}) = {$got}, expected {$expected}\n");
        exit(1);
    }
}

echo 'All ' . count($cases) . " checks passed.\n";