Solution.java

class Solution {
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        ListNode dummy = new ListNode(0);
        ListNode current = dummy;
        
        while (list1 != null && list2 != null) {
            if (list1.val < list2.val) {
                current.next = list1;
                list1 = list1.next;
            } else {
                current.next = list2;
                list2 = list2.next;
            }
            current = current.next;
        }
        
        // Attach the remaining nodes from the non-exhausted list
        if (list1 != null) current.next = list1;
        else current.next = list2;
        
        return dummy.next;  // Return the head of the merged list
    }
}