LeetCode 147: Insertion Sort List

/**
 * 147. Insertion Sort List
 * 1. Time:O(n2)  Space:O(1)
 * 2. Time:O(n2)  Space:O(1)
 */

// 1. Time:O(n2)  Space:O(1)
class Solution {
    public ListNode insertionSortList(ListNode head) {
        ListNode dummy = new ListNode(0);
        ListNode prev = dummy;
        ListNode cur = head;
        while(cur!=null){
            ListNode tmp = cur.next;
            while(prev.next!=null && prev.next.val<cur.val) prev = prev.next;
            cur.next = prev.next;
            prev.next = cur;
            prev = dummy;
            cur = tmp;
        }
        return dummy.next;
    }
}

// 2. Time:O(n2)  Space:O(1)
class Solution {
    public ListNode insertionSortList(ListNode head) {
        ListNode dummy = new ListNode(Integer.MIN_VALUE);
        ListNode prev = dummy;
        ListNode tail = dummy;
        ListNode cur = head;
        while(cur!=null){
            if(tail.val<cur.val){
                tail.next = cur;
                tail = cur;
                cur = cur.next;
            }else{
                ListNode tmp = cur.next;
                while(prev.next!=null && prev.next.val<cur.val) prev = prev.next;
                tail.next = tmp;
                cur.next = prev.next;
                prev.next = cur;
                prev = dummy;
                cur = tmp;
            }
        }
        return dummy.next;
    }
}