[leetCode][JS] 21. Merge Two Sorted Lists - recursion

🧦 Decription

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]

🧦 Solution

var mergeTwoLists = function(l1, l2) {
      if (l1 === null) {
        return l2;
    }
    
    if (l2 === null) {
        return l1;
    }
    
    if (l1.val < l2.val) {
        l1.next = mergeTwoLists(l1.next, l2);
            console.log(l1,l2)
        return l1;
    } else {
        l2.next = mergeTwoLists(l1, l2.next);
            console.log(l1,l2)
        return l2;
    }
};

아직 완전히 이해했다기에는 헷갈리는 부분이 있지만, 재귀함수를 이용한 풀이이다.

🧦 Result

• Runtime: 228 ms, faster than 5.22% of JavaScript online submissions for Merge Two Sorted Lists.
• Memory Usage: 45.9 MB, less than 5.01% of JavaScript online submissions for Merge Two Sorted Lists.

Reference

• https://leetcode.com/problems/merge-two-sorted-lists/discuss/1479757/Easy-to-Understand-Recursive-Solution