题解 | #单链表的排序#

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param head ListNode类 the head node
     * @return ListNode类
     */
    public ListNode sortInList (ListNode head) {
        // write code here
        if (head == null || head.next == null) {
            return head;
        }
        List<Integer> list = new ArrayList<>();
        while (head != null) {
            list.add(head.val);
            head = head.next;
        }
        int[] arr = new int[list.size()];
        for (int i = 0; i < arr.length; i++) {
            arr[i] = list.get(i);
        }
        quickSort(arr, 0, arr.length - 1);
        
        head = new ListNode(arr[0]);
        ListNode tail = head;
        for (int i = 1; i < arr.length; i++) {
            ListNode cur = new ListNode(arr[i]);
            tail.next = cur;
            tail = cur;
        }
        return head;
    }
    
    private void quickSort(int[] arr, int left, int right) {
        if (left < right) {
            int mid = partition(arr, left, right);
            quickSort(arr, left, mid - 1);
            quickSort(arr, mid + 1, right);
        }
    }
    
    private int partition(int[] arr, int left, int right) {
        int temp = arr[left];
        while (left < right) {
            while (left < right && arr[right] >= temp) {
                right--;
            }
            arr[left] = arr[right];
            while (left < right && arr[left] <= temp) {
                left++;
            }
            arr[right] = arr[left];
        }
        arr[left] = temp;
        return left;
    }
    
    
    
    
    
    
}