LeetCode 21. Merge Two Sorted Lists

Question

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.

Explanation

两个指针。非常简单。

Code

public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode a = l1;
        ListNode b = l2;
        if (l1 == null && l2 == null) return null;
        ListNode curr = new ListNode(0);
        ListNode dummy= curr;
        while(a != null && b != null) {
            if (a.val < b.val) {
                dummy.next = new ListNode(a.val);
                a = a.next;
            } else {
                dummy.next = new ListNode(b.val);
                b = b.next;
            }
            dummy = dummy.next;
        }
        if(a!= null) dummy.next = a;
        else dummy.next = b;
        return curr.next;
    }
}