> For the complete documentation index, see [llms.txt](https://jaywin.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jaywin.gitbook.io/leetcode/topics/linkedlist.md).

# LinkedList

## key points

* dummy node
* 2 pointers: fast and slow. `while(fast != null && fast.next != null) fast = head, slow = head, fast = fast.next.next, slow = slow.next`, slow stop in the middle or right middle.
* reverse: track at least 2 points
* cycle detection, 2 pointers, Floyd cycle

## Reverse

1. iterative: left + curr + right, 3 points
2. recursive: return last node

<https://leetcode.com/problems/reverse-linked-list/description/> <https://leetcode.com/problems/reverse-linked-list-ii/description/> <https://leetcode.com/problems/palindrome-linked-list/description/>

## Cycle

<https://leetcode.com/problems/linked-list-cycle/description/> <https://leetcode.com/problems/find-the-duplicate-number/description/>

## Intersection

<https://leetcode.com/problems/intersection-of-two-linked-lists/description/>

## Utilize the next node

<https://leetcode.com/problems/copy-list-with-random-pointer/description/>

## `+ - * /` etc operations

Key points: `carry` `curr % 10` `curr / 10` Start from right end plus max length `max(len1, len2) + 1`, multiply max length `len1 + len2`

### LinkedList

<https://leetcode.com/problems/add-two-numbers> <https://leetcode.com/problems/add-two-numbers-ii/description/> <https://leetcode.com/problems/plus-one-linked-list/description/>

### Array

<https://leetcode.com/problems/plus-one/discuss/>

### String

<https://leetcode.com/problems/multiply-strings/description/> <https://leetcode.com/problems/add-binary/description/> <https://leetcode.com/problems/add-strings/description/>

### Bit manipulation

<https://leetcode.com/problems/sum-of-two-integers/description/>

### Binary search

<https://leetcode.com/problems/sqrtx/description/> <https://leetcode.com/problems/powx-n/description/>

## Linked-List

* dummy node
* two pointers:

  ```java
  ListNode fast = head.next, slow = head;
  while (fast != null && fast.next != null) {
    fast = fast.next.next;
    slow = slow.next;
  }
  ```