84669 person learning
152542 person learning
20005 person learning
5487 person learning
7821 person learning
359900 person learning
3350 person learning
180660 person learning
48569 person learning
18603 person learning
40936 person learning
1549 person learning
1183 person learning
32909 person learning
$arr = array(2) { [0]=> array(3) { [0]=> string(1) "1" [1]=> string(1) "2" [2]=> string(1) "3" } [1]=> array(3) { [0]=> string(1) "4" [1]=> string(1) "5" [2]=> string(1) "6" } } //这种数组换成一维数组$arr1(14,15,16,24,25,26);count($arr)无限大，所有可能性，怎么弄
//排列组合 function zuhe($arr){ if(count($arr) >= 2){ $tmparr = array(); $arr1 = array_shift($arr); $arr2 = array_shift($arr); foreach($arr1 as $k1 => $v1){ foreach($arr2 as $k2 => $v2){ $tmparr[] = $v1.'_'.$v2; } } array_unshift($arr, $tmparr); $arr = zuhe($arr); }else{ return $arr; } return $arr; }
What does it mean? I don’t understand.
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
//排列组合 function zuhe($arr){ if(count($arr) >= 2){ $tmparr = array(); $arr1 = array_shift($arr); $arr2 = array_shift($arr); foreach($arr1 as $k1 => $v1){ foreach($arr2 as $k2 => $v2){ $tmparr[] = $v1.'_'.$v2; } } array_unshift($arr, $tmparr); $arr = zuhe($arr); }else{ return $arr; } return $arr; }What does it mean? I don’t understand.