$pivot = $arr[0];
    $n = count($arr);
    $left = $right = $equal = [];
    for($i=0;$i<$n;$i++){
        if($arr[$i] == $pivot){
            $equal[] = $arr[$i];
        }else if($arr[$i] < $pivot){
            $left[] = $arr[$i];
        }else{
            $right[] = $arr[$i];   
        }
    }
    
    $result = array_merge($left,$equal,$right);
    return $result;

 public static List<Integer> quickSort(List<Integer> arr) {
        Collections.sort(arr);
        return arr;
    }

from itertools import tee, chain

def quickSort(arr):
    equal = arr[0]
    t1, t2 = tee(arr)
    left = filter(lambda x: x < equal, t1)
    right = filter(lambda x: x > equal, t2)
    return chain(left, [equal], right)

func quickSort(arr: [Int]) -> [Int] {
    var leftArr: [Int] = []
    var equalArr: [Int] = []
    var rigthArr: [Int] = []
    let checkValue = arr[0]
    for item in arr {
        if item < checkValue {
            leftArr.append(item)
        } else if checkValue == item {
            equalArr.append(item)
        } else {
            rigthArr.append(item)
        }
    }
    return leftArr + equalArr + rigthArr
}

public static List<Integer> quickSort(List<Integer> arr) {
        
        List<Integer> left = new ArrayList<>();
        List<Integer> equal = new ArrayList<>();
        List<Integer> right = new ArrayList<>();
        
        int p = arr.get(0);
        
        for(int i = 0; i < arr.size(); i++) {
            int element = arr.get(i);
            
            if(element < p) {
                
                left.add(element);
            } else if (element > p) {
                
                right.add(element);
            } else {
                
                equal.add(element);
            }
        }
        
        left.addAll(equal);
        left.addAll(right);

        return left;
    }