public static void mergeSort(int[] a, int low, int high) { //呼叫mergeSort方法時low為0, high為a.length-1
		int mid = (low + high) / 2;
		if (low < high) {
			MergeSort(a, low, mid);
			MergeSort(a, mid + 1, high);
			merge(a, low, mid, high);
		}
	}

	public static void merge(int[] a, int low, int mid, int high) {
		int[] temp = new int[high - low + 1];
		int i = low;
		int j = mid + 1;
		int k = 0;
		while (i <= mid && j <= high) {
			if (a[i] < a[j])
				temp[k++] = a[i++];
			else
				temp[k++] = a[j++];
		}
		while (i <= mid)
			temp[k++] = a[i++];
		while (j <= high)
			temp[k++] = a[j++];
		for (int index = 0; index < temp.length; index++)
			a[index + low] = temp[index];
	}