PHP实现归并排序算法（代码实例）

<?php
function merge_sort($my_array){
    if(count($my_array) == 1 ) return $my_array;
    $mid = count($my_array) / 2;
    $left = array_slice($my_array, 0, $mid);
    $right = array_slice($my_array, $mid);
    $left = merge_sort($left);
    $right = merge_sort($right);
    return merge($left, $right);
}
function merge($left, $right){
    $res = array();
    while (count($left) > 0 && count($right) > 0){
        if($left[0] > $right[0]){
            $res[] = $right[0];
            $right = array_slice($right , 1);
        }else{
            $res[] = $left[0];
            $left = array_slice($left, 1);
        }
    }
    while (count($left) > 0){
        $res[] = $left[0];
        $left = array_slice($left, 1);
    }
    while (count($right) > 0){
        $res[] = $right[0];
        $right = array_slice($right, 1);
    }
    return $res;
}
$test_array = array(100, 54, 7, 2, 5, 4, 1);
echo "原始数组 : ";
echo implode(', ',$test_array );
echo "\n排序后数组:";
echo implode(', ',merge_sort($test_array))."\n";

原始数组 : 100, 54, 7, 2, 5, 4, 1 
排序后数组:1, 2, 4, 5, 7, 54, 100

array_slice ( array $array , int $offset [, int $length = NULL [, bool $preserve_keys = FALSE ]] ) : array