Insertion Sort List

Sort a linked list using insertion sort.

分析：插入排序处理链表。借助一个helper 头节点，来避免比较过程中插入位置在头节点处的情况。

/** * 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 initNode = new ListNode(head.val);        ListNode fakeHead = new ListNode(-1);        fakeHead.next = initNode;        ListNode fakeCursor = fakeHead;                head = head.next;        ListNode cursor = head;        while (cursor != null) {                        while (fakeCursor.next != null && cursor.val >= fakeCursor.next.val) {                fakeCursor = fakeCursor.next;            }                        head = cursor.next;                        if (fakeCursor.next != null) {                cursor.next = fakeCursor.next;                fakeCursor.next = cursor;            } else {                fakeCursor.next = cursor;                cursor.next = null;            }                        cursor = head;            fakeCursor = fakeHead;        }                return fakeHead.next;    }}