哑节点---Merge Two Sorted Lists

Merge two sorted (ascending) linked lists and return it as a new sorted list. The new sorted list should be made by splicing together the nodes of the two lists and sorted in ascending order.

Have you met this question in a real interview? Yes

Example

Given 1->3->8->11->15->null, 2->null , return 1->2->3->8->11->15->null.

public class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
ListNode dummy = new ListNode(0);
ListNode lastNode = dummy;

while (l1 != null && l2 != null) {
if (l1.val < l2.val) {
lastNode.next = l1;
l1 = l1.next;
} else {
lastNode.next = l2;
l2 = l2.next;
}
lastNode = lastNode.next;
}

if (l1 != null) {
lastNode.next = l1;
} else {
lastNode.next = l2;
}

return dummy.next;
}
}