[leetcode]Insertion Sort List-list 插入排序 java

注意以下几项

1. 题目没有说按从小打到排序

2. 排序的时候需要判断前驱为空，后继为空的情况

 

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
   public ListNode insertionSortList(ListNode head) {
        if(head == null){
            return head;
        }
        ListNode p = head.next;
        head.next = null;
        while (p!=null) {
            ListNode temp = p.next;
            ListNode sortP = head;
            ListNode sortPParent = null;
            int i = 0;
            while (sortP!=null){
                if(p.val < sortP.val){
                    if(sortPParent !=null){
                        sortPParent.next = p;
                    }
                    p.next = sortP;
                    if(i == 0){
                        head = p;
                    }
                    break;
                }
                sortPParent = sortP;
                if(sortP.next == null){
                    sortP.next=p;
                    p.next=null;
                    break;
                }
                sortP=sortP.next;
                i++;
            }
           p = temp;
        }
        return head;
    }
}