十大排序算法之冒泡排序（1）

1. 冒泡排序

<?php

/**
 * 原始冒泡排序
 */
function bubbleSort($sortData)
{
    $count = count($sortData);
    $sortCount = 0;
    
    for ($i = 0; $i < $count - 1; $i++) {
        for ($j = 0; $j < $count - $i - 1; $j++) {
            $sortCount++;
            if ($sortData[$j] > $sortData[$j + 1]) {
                $temp = $sortData[$j];
                $sortData[$j] = $sortData[$j + 1];
                $sortData[$j + 1] = $temp;
            }
        }
    }
    
    echo 'bubbleSort Count:' . $sortCount;
    echo PHP_EOL;
    return $sortData;
}

/**
 * 改进1：使用标识符标记某次循环是否交换了，没交换则直接终止（全部有序）
 * 
 */
function bubbleSort_2($sortData){
    $count = count($sortData);
    $sortCount = 0;
 
    $isChanged = true;
    for ($i = 0; $i < $count - 1 && $isChanged; $i++) {
        $isChanged = false;
        for ($j = 0; $j < $count - $i - 1; $j++) {
            $sortCount++;
            if ($sortData[$j] > $sortData[$j + 1]) {
                $temp = $sortData[$j];
                $sortData[$j] = $sortData[$j + 1];
                $sortData[$j + 1] = $temp;
                $isChanged = true;
            }
        }
    }

    echo 'bubbleSort_2 Count:' . $sortCount;
    echo PHP_EOL;
    return $sortData;
}

/**
 * 改进2：记录最后一次更改的位置，之后的不再进行比较（局部有序）
 * 
 */
function bubbleSort_3($sortData){
    $count = count($sortData);
    $sortCount = 0;
 
    $isChanged = true;
    $lastCount = $count - 1;
    for ($i = 0; $i < $lastCount && $isChanged; $i++) {
        $isChanged = false;
        for ($j = 0; $j < $lastCount - $i; $j++) {
            $sortCount++;
            $lastSort = $lastCount;
            if ($sortData[$j] > $sortData[$j + 1]) {
                $temp = $sortData[$j];
                $sortData[$j] = $sortData[$j + 1];
                $sortData[$j + 1] = $temp;
                $isChanged = true;
                $lastSort = $j;
            }
        }
        $lastCount = $lastSort;
    }

    echo 'bubbleSort_3 Count:' . $sortCount;
    echo PHP_EOL;
    return $sortData;
}

/**
 * 改进3：双向排序，从前往后记录最后一次排序的位置post1,从后往前记录最后一次排序的位置post2
 * 当post2 > post1的时候说明完成了
 */
function bubbleSort_4($sortData){
    $count = count($sortData);
    $post1 = $count-1;
    $post2 = 0;
    $index = 0;
    $sortCount = 0;
    while($post1 > $post2){
        for($i = $post2; $i < $post1; $i++){
            $sortCount++;
            if ($sortData[$i] >  $sortData[$i + 1]) {
                $temp = $sortData[$i];
                $sortData[$i] = $sortData[$i + 1];
                $sortData[$i + 1] = $temp;
                $index = $i;
            }
        }
        $post1 = $index;
        
         for($j = $post1; $j > $post2; $j--){
             if($sortData[$j - 1] > $sortData[$j]){
                $sortCount++;
                $temp = $sortData[$j];
                $sortData[$j] = $sortData[$j - 1];
                $sortData[$j - 1] = $temp;
                $index = $j; 
             }
        }
        $post2 = $index;
    }

    echo 'bubbleSort_4 Count:' . $sortCount;
    echo PHP_EOL;
    return $sortData;
}

$testSortData = [3, 2, 9, 234, 3432, 43, 22, 33, 21312, 123];

$sortResult = bubbleSort($testSortData);
echo 'bubbleSort Result:';
echo PHP_EOL;
echo(implode(',', $sortResult));
echo PHP_EOL;

$sortResult = bubbleSort_2($testSortData);
echo 'bubbleSort_2 Result:';
echo PHP_EOL;
echo(implode(',', $sortResult));

$sortResult = bubbleSort_3($testSortData);
echo 'bubbleSort_3 Result:';
echo PHP_EOL;
echo(implode(',', $sortResult));

$sortResult = bubbleSort_4($testSortData);
echo 'bubbleSort Result:';
echo PHP_EOL;
echo(implode(',', $sortResult));
echo PHP_EOL;