21. Merge Two Sorted Lists

[Luchanaaaaa]

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        ListNode dammy = new ListNode(0);
        ListNode cur = dammy;
        while (list1!= null|| list2!=null){
            if(list1 == null){
                cur.next = list2;
                break;
            }else if(list2 == null){
                cur.next = list1;
                break;
            }
            if(list1.val <= list2.val){
                cur.next = list1;
                list1 = list1.next;
            }else{
                cur.next = list2;
                list2 = list2.next;
            }
            cur = cur.next;
        }
        return dammy.next;

    }
}

[Luchanaaaaa]

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        ListNode pointer1 = list1;
        ListNode pointer2 = list2;

        ListNode dummy = new ListNode(-1);
        ListNode cur = dummy;

        while(pointer1 != null || pointer2 != null){

                if(pointer1 == null || pointer2 != null &&  pointer1.val > pointer2.val){
                    cur.next = new ListNode(pointer2.val);
                    pointer2 = pointer2.next;
                } 
                else{
                    cur.next = new ListNode(pointer1.val);
                    pointer1 = pointer1.next;
                } 
           
            cur = cur.next;
        }

        return dummy.next;
        
    }
}