leetcode-147. 对链表进行插入排序

题目

https://leetcode-cn.com/problems/insertion-sort-list/description/

代码

/*
 * @lc app=leetcode.cn id=147 lang=java
 *
 * [147] 对链表进行插入排序
 */

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

        ListNode result = new ListNode(head.val);
        head = head.next;

        while(head!=null){
            result=insertSort(result, head.val);
            head=head.next;
        }
        return result;
    }

    private ListNode insertSort(ListNode result, int val){
        ListNode p =result;
        ListNode pre = result;
        int flag=0;
        while(p!=null){
            if(p.val > val){
                ListNode listNode = new ListNode(val);
                if(flag==0){
                    listNode.next=result;
                    return listNode;
                }else{
                    pre.next=listNode;
                    listNode.next=p;
                    return result;
                }
            }else{
                if(flag==0){
                    p=p.next;
                    flag=1;
                }else{
                    p=p.next;
                    pre=pre.next;
                }
            }
        }
        ListNode tailNode = new ListNode(val);
        pre.next=tailNode;
        return result;
    }

}
// @lc code=end