排序算法之快速排序

时间复杂度：平均O(nlogn)  最好O(nlogn)  最坏O(n²)

空间复杂度：O(logn)

稳定性：不稳定

特点：n大时较好

public class QuickSort {

	public static void main(String[] args) {
		int[] a = { 2, 7, 8, 3, 1, 6, 9, 0, 5, 4 };
		quickSort(a, 0, a.length - 1);
		for (int n : a) {
			System.out.print(n + " ");
		}
	}

	public static void quickSort(int[] a, int low, int high) {
		if (a == null) {
			return;
		}
		if (low >= high) {
			return;
		}
		int i, j, n;
		i = low;
		j = high;
		n = a[i];
		while (i < j) {
			while (i < j && a[j] >= n) {
				j--;
			}
			if (i < j) {
				a[i++] = a[j];
			}
			while (i < j && a[i] < n) {
				i++;
			}
			if (i < j) {
				a[j--] = a[i];
			}
		}
		a[i] = n;
		quickSort(a, low, i - 1);
		quickSort(a, i + 1, high);
	}

}