js排序算法05——快速排序

function quickSort(arr,left,right){
    if(right-left<=1){
        return arr;
    }
    else{
        var l=left,r=right,m=parseInt((r+l)/2);        
        var pivot,cup;
        if(arr[l]>arr[m]){
            cup = arr[m];
            arr[m] = arr[l];
            arr[l] = cup;
        }
        if(arr[m]>arr[r]){
            cup = arr[m];
            arr[m] = arr[r];
            arr[r] = cup;
        }
        if(arr[l]>arr[m]){
            cup = arr[m];
            arr[m] = arr[l];
            arr[l] = cup;
        }
        pivot = arr[m];
        cup = arr[r-1];
        arr[r-1] = arr[m];
        arr[m] = cup;
        var i=0,j=r-2;
        while(i<j){
            while(arr[i]<pivot){
                i++;
            }
            while(arr[j]>pivot){
                j--;
            }
            if(i<=j){
                cup = arr[i];
                arr[i] = arr[j];
                arr[j] = cup;
                i++;
                j--;
            }
        }
        cup = arr[i];
        arr[i] = arr[r-1];
        arr[r-1] = cup;
        quickSort(arr,l,i-1);
        quickSort(arr,i,r);
        return arr;    
    }
}