Merge Two Sorted Lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

/**
 * 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) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ListNode root = new ListNode(-1);
        ListNode cur1 = l1;
        ListNode cur2 = l2;
        ListNode cur3 = root;
        while(cur1 != null && cur2 != null){
            if(cur1.val < cur2.val){
                cur3.next = cur1;
                cur3 = cur1;
                cur1 = cur1.next;
            }else{
                cur3.next = cur2;
                cur3 = cur2;
                cur2 = cur2.next;
            }
        }
        if(cur1 == null){
            cur3.next = cur2;
        }
        if(cur2 == null){
            cur3.next = cur1;
        }
        return root.next;
    }
}

 第三遍：

/**
 * 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 header = new ListNode(-1);
        ListNode cur = header, cur1 = l1, cur2 = l2;
        while(cur1 != null || cur2 != null){
            int aa = cur1 != null ? cur1.val : Integer.MAX_VALUE;
            int bb = cur2 != null ? cur2.val : Integer.MAX_VALUE;
            if(aa > bb){
                cur.next = cur2;
                cur2 = cur2.next;
                cur = cur.next;
            } else {
                cur.next = cur1;
                cur1 = cur1.next;
                cur = cur.next;
            }
        }
        return header.next;
    }
}