private static void quickSort(char[] arr, int low, int high) {
		int i = low, j = high;
		int pivot = arr[low + (high - low)/2];
		while(i <= j) {
			while(arr[i] < pivot)
				i++;
			while(arr[j] > pivot)
				j--;
			if(i <= j) {
				exchange(arr, i, j);
				i++;
				j--;
			}
		}
		if(low < j)
			quickSort(arr, low, j);
		if(i < high)
			quickSort(arr, i, high);
	}