1.冒泡排序

function bubbleSort ($array) {
    $n = count($array);

    for ($i = 0; $i < $n -1; ++$i) {
        $swap = false;
        for ($j = 0; $j < $n - 1 - $i; ++$j) {
            if ($array[$j] > $array[$j + 1]) {
                $temp = $array[$j];
                $array[$j] = $array[$j + 1];
                $array[$j + 1] = $temp;
                $swap = true;
            }

        }
        if (!$swap) {
            break;
        }

    }

    return $array;
}

2.快速排序

<?php

function quickSort($array)
{
    if (count($array) <= 1) {
        return $array;
    }

    $mid   = $array[0];
    $left  = [];
    $right = [];

    for ($i = 1; $i < count($array); $i++) {
        if ($array[$i] < $mid) {
            $left[] = $array[$i];
        } else {
            $right[] = $array[$i];
        }
    }

    $left = quickSort($left);
    $right = quickSort($right);

    return array_merge($left, [$mid], $right);
}

$array = [2, 1, 10, 5, 6, 12, 33, 3];

echo json_encode(quickSort($array));

3.二分查找（必须有序）

<?php

function binarySearch($array, $search)
{
    $left  = 0;
    $right = count($array) - 1;

    while ($left <= $right) {
        $key = intval(($left + $right) / 2);
        $mid = $array[$key];
        if ($search == $mid) {
            return $key;
        }

        if ($search > $mid) {
            $left = $key + 1;
        }

        if ($search < $mid) {
            $right = $mid - 1;
        }
    }

    return -1;
}

$array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

echo binarySearch($array, 6);

4.归并排序

<?php
function mergeSort(array $array) {
    // 如果数组长度小于等于1，直接返回
    if (count($array) <= 1) {
        return $array;
    }

    // 分割数组
    $mid = floor(count($array) / 2);
    $left = mergeSort(array_slice($array, 0, $mid));
    $right = mergeSort(array_slice($array, $mid));

    // 合并已排序的子数组
    return merge($left, $right);
}

function merge(array $left, array $right) {
    $result = [];

    echo "left: " . json_encode($left) . "\r\n";
    echo "right: " . json_encode($right) . "\r\n------\r\n";

    while (count($left) > 0 && count($right) > 0) {
        if ($left[0] < $right[0]) {
            $result[] = array_shift($left);
        } else {
            $result[] = array_shift($right);
        }
    }

    return array_merge($result, $left, $right);
}

// 示例用法
$array = [38, 27, 43, 3, 9, 82, 10];
$sortedArray = mergeSort($array);
print_r($sortedArray); // 输出: [3, 9, 10, 27, 38, 43, 82]