LinkedList

1. Reverse Linked List

Array

1D Array

1. ⭐ Sort Array By Parity II: Trick about Even or Odd!
2. 🔥 Find All Duplicates in an Array: 1) How to use "1" and "2" 2) How to use the relation between key and value.
3. Queue Reconstruction by Height: Trick about Maximum.
4. Single Element in a Sorted Array: Binary Search.

2D Array

Traversal

1. Spiral Matrix III.

Recursion

1. Number of Enclaves.

Math

1. 🔥Two City Scheduling:Tricks about "Sum".

2 Array

1. Interval List Intersections.

Tree

Iteration

1. N-ary Tree Preorder Traversal
2. N-ary Tree Postorder Traversal
3. Binary Tree Inorder Traversal

Recursion

1. 🔥 Distribute Coins in Binary Tree: Tricks about 1) Move 2) Equal to "Decision".Learn a lot from Lee215.
2. Flip Equivalent Binary Trees: Two Trees.
3. Trim a Binary Search Tree: Change the way in which nodes link.
4. Maximum Difference Between Node and Ancestor: Maxima and Minima during the recursion.

DFS && BFS

1. 🔥 Maximum Depth of N-ary Tree: 1) BFS On each layer, we count how many nodes there 2) The relation about each recursion.

Graph

Traversal

1. All Paths From Source to Target: Recursion and Stack implemented by array.

Backtrack

2D Array

1. Unique Paths III: Recursion.

Greedy

1D Array

1. ⭐ Maximize Sum Of Array After K Negations: Lee215.

2D Array

1. Score After Flipping Matrix: Lee215 is awesome!Without modifing matrix in reality, we can still obtain highest score.

DP

1D Array

1. Longest Arithmetic Sequence: Lee215 uses "max".
2. Daily Temperatures

2D Array

1. Minimum Falling Path Sum.

Operator

1. Counting Bits.
2. Single Number: How to use "1" and "2".
3. ⭐ Single Number III