function fQuickSort(arr,low,high) {
    if(low >= high){
        throw new Error(‘low should less than high‘);
    }
    var pivotIndex = fSwapInPlace(arr,low,high);
    fQuickSort(arr,low,pivotIndex-1);
    fQuickSort(arr,pivotIndex+1,high);
}

function fSwapInPlace(arr,low,high){
    var pivot = arr[low];
    while (low < high) {
        while(low < high && arr[high] > pivot){
            high--;
        }
        arr[low] = arr[high];
        while(low < high && arr[low] <= pivot){
            low++;
        }
        arr[high] = arr[low];
    }
    arr[low] = pivot;
　　 //stop at pivot place,low equals pivot index
    return low;
}