LeetCode Insertion Sort List

原题链接在这里：https://leetcode.com/problems/insertion-sort-list/

题目：

Sort a linked list using insertion sort.

题解：

与Sort List类似.

当出现cur.val > cur.next.val时就需要insert cur.next到对应位置了. 由mark来找对应的位置.

Time Complexity: O(n^2). Space: O(1).

AC Java:

/**
* 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 = head;
ListNode mark = dummy;
ListNode cur = head;
while(cur.next != null){
if(cur.val > cur.next.val){ //当出现前一个点val 比后一个点val大时，就要找到mark 的下一位来添加大的点
while(mark.next.val < cur.next.val){ //找mark位置
mark = mark.next;
}
ListNode temp = cur.next;
cur.next = cur.next.next;
temp.next = mark.next;
mark.next = temp;
mark = dummy;   //mark回到dummy位置
}else{
cur = cur.next;
}
}
return dummy.next;
}
}