题解 | #对链表进行插入排序#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode insertionSortList (ListNode head) {
        // write code here
        if (null == head.next) {
            return head;
        }
        int len = 0; // 定义一个整型变量，用于存放链表的长度
        ListNode node = head;
        while (null != node) {
            len++;
            node = node.next;
        }
        int[] arr = new int[len];
        int index = 0;
        node = head;
        while (null != node) {
            arr[index] = node.val;
            index++;
            node = node.next;
        }
        quickSort(arr, 0, arr.length - 1);
        node = head;
        for (int num : arr) {
            node.val = num;
            node = node.next;
        }
        return head;
    }
    
    public void quickSort(int[] arr, int start, int end) {
        if (start >= end) {
            return;
        }
        int l = start - 1;
        int r = end + 1;
        int p = start;
        int val = arr[end];
        while (p < r) {
            if (arr[p] < val) {
                int swap = arr[p];
                arr[p] = arr[l + 1];
                arr[l + 1] = swap;
                l++;
                p++;
            }
            else if (arr[p] > val) {
                int swap = arr[p];
                arr[p] = arr[r - 1];
                arr[r - 1] = swap;
                r--;
            }
            else {
                p++;
            }
        }
        quickSort(arr, start, l);
        quickSort(arr, r, end);
    }
}