在PHP和Python中进行冒泡排序 [英] Bubble Sort in PHP and Python

问题描述

据我所知，这两个程序应该做的完全一样。但是，Python版本有效，而PHP版本无效。我想念什么？

As far as I can tell, these two programs should do exactly the same thing. However, the Python version works and the PHP one doesn't. What am I missing please?

def bubbleSort(alist):
    for passnum in range(len(alist)-1,0,-1):
        for i in range(passnum):
            if alist[i]>alist[i+1]:
                temp = alist[i]
                alist[i] = alist[i+1]
                alist[i+1] = temp

my_list = [2,3,5,4,1]
bubbleSort(my_list)
print(my_list)

---

---

<?php
// Bubble Sort
$my_list = [2,3,5,4,1];

function bubble_sort($arr){
    $size = count($arr);
    for($pass_num = $size - 1; $pass_num >= 0; $pass_num--){
        for($i = 0; $i < $pass_num; $i++){
            if($arr[i] > $arr[$i + 1]){
                swap($arr, $arr[i], $arr[$i+1]);
            }
        }
    }
}


function swap(&$arr, $a, $b) {
    $tmp = $arr[$a];
    $arr[$a] = $arr[$b];
    $arr[$b] = $tmp;
}

bubble_sort($my_list);
print_r ($my_list);

推荐答案

排序实际上是可行的，但您却不这样做传递对 bubble_sort（$ arr）函数的引用，您将永远看不到实际结果。告诉 bubble_sort（）通过引用传递数组意味着您正在更改 $ my_list 而不是 $ my_list

The sort is in fact working, but as you dont pass a reference to the bubble_sort($arr) function you never get to see the actual result. Telling bubble_sort() that the array is being passed by reference means you are changing $my_list and not a copy of $my_list

哦，您使用 $ arr [i] 而不是 $ arr [$ i]

// Bubble Sort
$my_list = [2,3,5,4,1];

function bubble_sort(&$arr){    // <-- changed to &$arr
    $size = count($arr);
    for($pass_num = $size - 1; $pass_num >= 0; $pass_num--){
        for($i = 0; $i < $pass_num; $i++){
            if($arr[$i] > $arr[$i + 1]){
                // also changed this line to pass just the indexes
                swap($arr, $i, $i+1);   
            }
        }
    }
}


function swap(&$arr, $a, $b) {
    $tmp = $arr[$a];
    $arr[$a] = $arr[$b];
    $arr[$b] = $tmp;
}

bubble_sort($my_list);
print_r ($my_list);

如果要在关闭错误报告的实时服务器上进行测试，请将这些行添加到顶部

If you are testing this on a live server where error reporting is turned off add these lines to the top of any script you are developing, while you are developing it.

<?php
error_reporting(E_ALL); 
ini_set('display_errors', 1);

编译错误将显示在网页上

And the compile errors would have shown on the web page

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