147. Insertion Sort List

Sort a linked list using insertion sort.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution
    public ListNode insertionSortList(ListNode head) {
        ListNode dummy = new ListNode(0);
        // 这个dummy的作用是，把head开头的链表一个个的插入到dummy开头的链表里
        // 所以这里不需要dummy.next = head;

        while (head != null) {
            ListNode node = dummy;
            while (node.next != null && node.next.val < head.val) {
                node = node.next;
            }
            ListNode temp = head.next;
            head.next = node.next;
            node.next = head;
            head = temp;
        }

        return