merge 2 lists.java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {		
		ListNode head = null;
        ListNode current = head;
        int count = 0;
        
        while (l1 != null || l2 != null) {
        	ListNode node = new ListNode(0);
        	count++;
        	
        	if (l1 != null && l2 != null) {
        		if (l1.val <= l2.val) {
        			node.val = l1.val;
        			l1 = l1.next;
        		} else {
        			node.val = l2.val;
        			l2 = l2.next;
        		}
        	} else if (l1 != null) {
        		node.val = l1.val;
        		l1 = l1.next;
        	} else {
        		node.val = l2.val;
        		l2 = l2.next;
        	}
        	
        	if (count == 1) {
        		head = node;
        		current = node;
        	} else { 
        		current.next.val = node.val;
        		current = current.next;
        	}
        	current.next = new ListNode(0);
        }
        
        if (current != null)
            current.next = null;
        return head;
    }
}