leetCode - Merge Two Sorted Lists

문제

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

 

Example 1:

Input: l1 = [1,2,4], l2 = [1,3,4] Output: [1,1,2,3,4,4]

Example 2:

Input: l1 = [], l2 = [] Output: []

Example 3:

Input: l1 = [], l2 = [0] Output: [0]

 

Constraints:

• The number of nodes in both lists is in the range [0, 50].
• -100 <= Node.val <= 100
• Both l1 and l2 are sorted in non-decreasing order.

 

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풀이

const mergeTwoLists = function (l1, l2) {
    let nullHead = new ListNode(null);
    let current = nullHead;
    while (l1 || l2) {
        if (!l2 || (l1 && (l1.val < l2.val))) {
            current.next = l1;
            current = current.next;
            l1 = l1.next
        } else {
            current.next = l2;
            current = current.next;
            l2 = l2.next
        }
    }
    return nullHead.next;
};