快排

void quickSort(int * const a, int startIndex, int endIndex)
{
	int s = startIndex;
	int e = endIndex;
	if (endIndex == startIndex )
		return;
	endIndex--;
	while (startIndex < endIndex)
	{
		int temp = a[startIndex];
		while (startIndex < endIndex)
		{
			if (a[endIndex] <= temp)
			{
				break;
			}
			endIndex--;
		}
		if (startIndex < endIndex)
		{
			//有比startIndex位置小的数
			a[startIndex] = a[endIndex];
			a[endIndex] = temp;
		}
		//从startIndex开始往后找,找一个比temp大的数,此时endIndex上放的是temp
		temp = a[endIndex];
		startIndex++;
		while (startIndex < endIndex)
		{
			if (a[startIndex] > temp)
			{
				break;
			}
			startIndex++;
		}
		if (startIndex < endIndex)
		{
			a[endIndex] = a[startIndex];
			a[startIndex] = temp;
		}
	}
	//递归
	quickSort(a, s, startIndex);
	quickSort(a, startIndex + 1, e);
}