1669. Merge In Between Linked Lists

Description

You are given two linked lists: list1 and list2 of sizes n and m respectively.

Remove list1's nodes from the ath node to the bth node, and put list2 in their place.

The blue edges and nodes in the following figure indicate the result:

Build the result list and return its head.

 

Example 1:

Input: list1 = [0,1,2,3,4,5], a = 3, b = 4, list2 = [1000000,1000001,1000002]
Output: [0,1,2,1000000,1000001,1000002,5]
Explanation: We remove the nodes 3 and 4 and put the entire list2 in their place. The blue edges and nodes in the above figure indicate the result.

Example 2:

Input: list1 = [0,1,2,3,4,5,6], a = 2, b = 5, list2 = [1000000,1000001,1000002,1000003,1000004]
Output: [0,1,1000000,1000001,1000002,1000003,1000004,6]
Explanation: The blue edges and nodes in the above figure indicate the result.

 

Constraints:

• 3 <= list1.length <= 104
• 1 <= a <= b < list1.length - 1
• 1 <= list2.length <= 104

 

Solutions

Solution: Linked List

• Time complexity: O(n)
• Space complexity: O(1)

 

JavaScript

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} list1
 * @param {number} a
 * @param {number} b
 * @param {ListNode} list2
 * @return {ListNode}
 */
const mergeInBetween = function (list1, a, b, list2) {
  let currentNode = list1;
  let current = 0;
  let leftNode = (rightNode = null);

  while (current <= b) {
    if (current === a - 1) leftNode = currentNode;
    currentNode = currentNode.next;
    current += 1;
  }
  rightNode = currentNode;
  leftNode.next = list2;

  while (leftNode.next) leftNode = leftNode.next;
  leftNode.next = rightNode;
  return list1;
};