1669. Merge In Between Linked Lists

Medium

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 <= 10^4

• 1 <= a <= b < list1.length - 1

• 1 <= list2.length <= 10^4

解題

func mergeInBetween(list1 *ListNode, a int, b int, list2 *ListNode) *ListNode {
    cur1, cur2 := list1, list2
    a1, b1 := list1, list1
    
    index := 0
    for cur1 != nil{
        if index == a - 1{
            a1 = cur1
        } else if index == b {
            b1 = cur1.Next
            break
        }

        cur1 = cur1.Next
        index++
    }

   a1.Next = cur2
   for cur2 != nil{
       if cur2.Next == nil{
           cur2.Next = b1
           break
       }
       cur2 = cur2.Next     
    } 
    return list1
}