Leetcode Insertion Sort List 插入排序链表

题目：

Sort a linked list using insertion sort.

分析：

1. 创建一个新的链表。

2. 对原链表中的每个元素，从新链表表头开始找该元素插入的位置，找到后插入元素。

Java代码实现：

/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode insertionSortList(ListNode head) {
if(head == null || head.next == null)
return head;

ListNode dummy = new ListNode(0);
dummy.next = new ListNode(head.val);
head = head.next;
ListNode node = dummy.next;
ListNode pre = dummy;

while(head!=null)
{
while(node!=null && head.val>=node.val)
{
pre = node;
node = node.next;
}
pre.next = new ListNode(head.val);
pre.next.next = node;
node = dummy.next;
pre = dummy;
head = head.next;
}

return dummy.next;
}
}