Merge Two Sorted Lists Easy 0 attempts
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Merge Two Sorted Lists

Easy Linked List LeetCode

Combine two already-sorted linked lists into a single sorted list.

Input Format
Implement mergeTwoLists(l1, l2). Inputs below show JavaScript function arguments; there is no stdin parsing. Linked lists use value arrays. The editor passes nodes with val and next properties; [] becomes null.
Output Format
Return the result described in the statement. Returned list heads are displayed as value arrays; a null head is [].

Sample Input and Output

Example 1 ยท Run Sample

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

Example 2

Input
l1 = []
l2 = []
Output
[]
Constraints
  • 0 to 50 nodes per list
  • -100 <= Node.val <= 100
Test Cases (2)
Case 1
Args: [[1,2,4],[1,3,4]] Expected: [1,1,2,3,4,4]
Case 2
Args: [[],[]] Expected: []
Topics
Linked List

Iterative Merge

javascript
function mergeTwoLists(l1, l2) {
  const dummy = {val: 0, next: null};
  let curr = dummy;
  while (l1 && l2) {
    if (l1.val <= l2.val) { curr.next = l1; l1 = l1.next; }
    else { curr.next = l2; l2 = l2.next; }
    curr = curr.next;
  }
  curr.next = l1 || l2;
  return dummy.next;
}

Time: O(m + n) | Space: O(1)

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JavaScript