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:

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