#1669 - Merge In Between Linked Lists

Medium • View on LeetCode • View on GitHub

Problem 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:

Solution

/**
 * 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}
 */
var mergeInBetween = function(list1, a, b, list2) {
  const result = new ListNode(0, list1);

  for (let i = 1; i < a; i++) {
    list1 = list1.next;
  }
  let tail = list1.next;
  list1.next = list2;
  for (let i = a; i < b; i++) {
    tail = tail.next;
  }
  while (list1 && list1.next) {
    list1 = list1.next;
  }
  list1.next = tail.next;

  return result.next;
};