java实现的快速排序小示例

Posted 2021-12-13 Neo_Gamer

写了个快速排序，结果是正确的，达到预期，请各路朋友指教。

/**
 * 快速排序示例，先选定基准值，比基准值大的放在右边，比基准值小的在左边
 * 右边先比较，再左边比较，再右边比较，再左边比较......
 *
 * @author x_wq
 * @date   2021/11/11 14:47
 */
public class QuickSortDemo {

    public static void main(String[] args) {
        int[] array = {12, 7, 20, 13, 34, 9, 18, 25, 6};
        quick(array, 0, array.length - 1);
        System.out.println(Arrays.toString(array));
    }

    private static void quick(int[] array, int start, int end) {
        int tmp = array[start];
        int tmpIndex = 0;

        int left = start;
        int right = end;
        while (left < right) {
            // 右边遍历
            while (array[right] >= tmp && right > left) {
                right --;
            }
            array[left ++] = array[right];
            if (right == left - 1) {
                tmpIndex = right;
                break;
            }

            // 左边遍历
            while (array[left] <= tmp && left < right) {
                left ++;
            }
            array[right --] = array[left];
            if (left == right + 1) {
                tmpIndex = left;
                break;
            }

        }
        array[tmpIndex] = tmp;

        // 以当前基准值将数组分成两部分，继续循环
        int leftIndex = tmpIndex - 1;
        int rightIndex = tmpIndex + 1;
        if (leftIndex > 0 && leftIndex > start) {
            quick(array, start, leftIndex);
        }
        if (rightIndex < array.length - 1 && rightIndex < end) {
            quick(array, rightIndex, end);
        }
    }
}