Examples to explain how to use PHP to achieve full arrangement

In computer science, a total permutation is a different permutation and combination of all elements in a set. The total permutation problem is a classic algorithm problem that can be used not only in mathematics and computer science, but also in other fields, such as cryptography, bioinformatics, and e-commerce.

Achieving full arrangement in PHP requires the use of recursive methods and techniques for exchanging elements. Below we will explain in detail how to use PHP to achieve full arrangement.

First, we need to define a function to implement the full arrangement operation. The function needs to receive two parameters. The first parameter is the array to be arranged, and the second parameter is the starting position of the array. The code is as follows:

function permute($arr, $start = 0) {
    // 获取数组长度
    $len = count($arr);
    
    // 如果起始位置等于数组长度，表示排列完成
    if ($start == $len - 1) {
        // 打印排列结果
        echo implode(' ', $arr) . "\n";
    } else {
        // 循环排列剩下的元素
        for ($i = $start; $i < $len; $i++) {
            // 交换起始元素和当前元素
            swap($arr, $start, $i);
            // 递归排列剩下的元素
            permute($arr, $start + 1);
            // 交换回来，保证数组不变
            swap($arr, $start, $i);
        }
    }
}

In the above code, we use a swap function, which is used to exchange the values ​​​​of two elements. The code is as follows:

function swap(&$arr, $i, $j) {
    $temp = $arr[$i];
    $arr[$i] = $arr[$j];
    $arr[$j] = $temp;
}

Then, we can use The permute function is used to implement the full arrangement operation. The code is as follows:

$originalArr = [1, 2, 3];
permute($originalArr);

In the above code, we first define an array containing three elements, and then pass it as a parameter to the permute function to generate a full arrangement of the entire array.

The complete code is as follows:

function permute($arr, $start = 0) {
    // 获取数组长度
    $len = count($arr);
    
    // 如果起始位置等于数组长度，表示排列完成
    if ($start == $len - 1) {
        // 打印排列结果
        echo implode(' ', $arr) . "\n";
    } else {
        // 循环排列剩下的元素
        for ($i = $start; $i < $len; $i++) {
            // 交换起始元素和当前元素
            swap($arr, $start, $i);
            // 递归排列剩下的元素
            permute($arr, $start + 1);
            // 交换回来，保证数组不变
            swap($arr, $start, $i);
        }
    }
}

function swap(&$arr, $i, $j) {
    $temp = $arr[$i];
    $arr[$i] = $arr[$j];
    $arr[$j] = $temp;
}

$originalArr = [1, 2, 3];
permute($originalArr);

The above is the method of using PHP to achieve full arrangement. The specific implementation can be adjusted and improved according to actual needs.

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