这个问题很简单，但让我头疼，例如，我有一个4个数字的数组，但最多可以有20个数字。按以下顺序给出：
[1] [2] [4] [5]
我需要获得这些数字的所有组合，除了数字不能排列，所以顺序是保持的，我将举一个我试图获得的例子：
[1] [ ] [4] [5]
[1] [2] [ ] [5]
[ ] [2] [4] [5]
[ ] [ ] [ ] [5]
and even
[ ] [ ] [ ] [ ]
所得数组将包含所得数字的子数组
更新：空数组是可选的，
[1] [4]
Or
[2] [4] [5]
也可以，并发症更少。
如果您意识到我们想要完成的实际上是递归的，那么您想要做的事情可以很容易地完成。对于每个子部分，我们需要做出选择：我们添加一个空格，或者从列表中添加一个数字。
function wonkyPermutations( $numbers ) {
return wonkyPermutationsWithSpaces( Array(), $numbers, count( $numbers ) );
}
function wonkyPermutationsWithSpaces( $prefix, $numbers, $maxlength ) {
if( $maxlength == 0 ) {
//We can't add anymore
return Array( $prefix );
} else {
//We have two choices: We either add a space, or we don't.
$prefix1 = $prefix;
$prefix1[] = NULL;
$prefix2 = $prefix;
$prefix2[] = $numbers[0];
$suffix1 = wonkyPermutationsWithSpaces( $prefix1, array_slice( $numbers, 1 ), $maxlength - 1 );
$suffix2 = wonkyPermutationsWithSpaces( $prefix2, array_slice( $numbers, 1 ), $maxlength - 1 );
return array_merge( $suffix1, $suffix2 );
}
}
$a = Array( 1, 2, 3, 4 );
var_dump( wonkyPermutations( $a ) );
基本上，我所做的是用这个答案的代码找出所有可能的"数字在那里"/"数字不在那里"组合，如下所示：
0 0 0 0
1 0 0 0
1 1 0 0
1 1 1 0
1 1 1 1
0 1 0 0
and so on...
之后，我将其应用于input数组内容。
<?php
//First of all, find out all possible combinations of "number is there" and "number is not there"
$input = ["1","2","4","5"];
$empty = " "; //Value to insert if "number is not there"
$length = sizeof($input); //How many numbers are in the array
$combinations = pow(2, $length); //Number of possible 1/0 combinations
$sequence = array();
for($x = 0; $x < $combinations; $x++) {
$sequence[$x] = str_split(str_pad(decbin($x), $length, 0, STR_PAD_LEFT));
}
//Alright, so now we have to apply these combinations to our $input array
$output = [];
foreach($sequence as $combo){
$output_combo = [];
foreach($combo as $key=>$val){
if ($val == 1){
//"number is there"
array_push($output_combo, $input[$key]);
}else{
//"number is not there"
array_push($output_combo, $empty);
}
}
array_push($output, $output_combo);
}
//There you go! The variable $output contains your array.
//Display the array (You can leave this part out...)
foreach($output as $combo){
foreach($combo as $val){
echo "[" . $val . "] ";
}
echo "<br>";
}
?>
看看这个PHPFiddle-它可以使用你想要的任意数量的数字。只要确保$empty变量包含您想要的值（如果数字不存在）。
只需点击此链接并选择"跑步"：http://phpfiddle.org/main/code/fdtn-u5jv