package g0001_0100.s0021_merge_two_sorted_lists;

// #Easy #Top_100_Liked_Questions #Top_Interview_Questions #Linked_List #Recursion
// #Data_Structure_I_Day_7_Linked_List #Algorithm_I_Day_10_Recursion_Backtracking
// #Level_1_Day_3_Linked_List #Udemy_Linked_List
// #2022_06_14_Time_1_ms_(69.17%)_Space_43.1_MB_(38.82%)

import com_github_leetcode.ListNode;

/*
 * 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; }
 * }
 */
public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode list = new ListNode(-1);
        ListNode head = list;
        while (l1 != null || l2 != null) {
            if (l1 != null && l2 != null) {
                if (l1.val <= l2.val) {
                    list.next = new ListNode(l1.val);
                    l1 = l1.next;
                } else {
                    list.next = new ListNode(l2.val);
                    l2 = l2.next;
                }
            } else if (l1 != null) {
                list.next = new ListNode(l1.val);
                l1 = l1.next;
            } else {
                list.next = new ListNode(l2.val);
                l2 = l2.next;
            }
            list = list.next;
        }
        return head.next;
    }
}
