[Leetcode] Insertion Sort List

Sort a linked list using insertion sort.

Solution:

/**
 * 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||head.next==null)
            return head;
        ListNode dummy=new ListNode(-1);
        ListNode pre,next;
        while(head!=null){
            pre=findPosition(dummy,head.val);
            next=pre.next;
            pre.next=new ListNode(head.val);
            pre.next.next=next;
            head=head.next;
        }
        return dummy.next;
    }

    private ListNode findPosition(ListNode dummy, int val) {
        // TODO Auto-generated method stub
        ListNode pre=dummy, next=pre.next;
        while(next!=null&&next.val<=val){
            next=next.next;
            pre=pre.next;
        }
        return pre;
    }
}