【LeetCode】Insertion Sort List

Sort a linked list using insertion sort.

//用到O（N）的额外空间
public class Solution {
    public ListNode insertionSortList(ListNode head) {
        if(head==null||head.next==null)
            return head;
        ListNode root = new ListNode(head.val);
        ListNode cur = head.next;
        while(cur!=null){
            ListNode tempNode = root;
            ListNode pre = root;
            while(tempNode!=null){
                if(cur.val>tempNode.val){
                    pre=tempNode;
                    tempNode=tempNode.next;
                }else{
                    break;
                }
            }           
            if(tempNode==root){
                ListNode newNode = new ListNode(cur.val);
                newNode.next=root;
                root=newNode;
                cur=cur.next;
            }else if(tempNode==null){
                ListNode newNode = new ListNode(cur.val);
                pre.next=newNode;
                cur=cur.next;
            }else{
                ListNode newNode = new ListNode(cur.val);
                pre.next=newNode;
                newNode.next=tempNode;
                cur=cur.next;
            }
            
            
        }
        
        return root;
        
    }
}

public class NSolution {
    public ListNode insertionSortList(ListNode head) {
        if(head==null||head.next==null)
            return head;
        
        ListNode cur = head.next;
        head.next=null;
        while(cur!=null){
            ListNode tempNode = head;
            ListNode pre = head;
            while(tempNode!=null){
                if(cur.val>tempNode.val){
                    pre=tempNode;
                    tempNode=tempNode.next;
                }else{
                    break;
                }
            }           
            if(tempNode==head){
                ListNode newNode = new ListNode(cur.val);
                newNode.next=head;
                head=newNode;
                cur=cur.next;
                
                
                
            }else if(tempNode==null){
                ListNode newNode = new ListNode(cur.val);
                pre.next=newNode;
                cur=cur.next;
            }else{
                ListNode newNode = new ListNode(cur.val);
                pre.next=newNode;
                newNode.next=tempNode;
                cur=cur.next;
            }
            
            
        }
        
        return head;
        
    }
}