HackMD
Two Pointers Study Guide
Basic Two Pointers
Same Direction Pointers
Problems where both pointers move in the same direction.
- 🟩 26. Remove Duplicates from Sorted Array [Solution]
- 🟩 27. Remove Element [Solution]
- 🟨 80. Remove Duplicates from Sorted Array II [Solution]
- 🟩 283. Move Zeroes [Solution]
- 🟩 88. Merge Sorted Array [Solution]
- 🟩 217. Contains Duplicate [Solution]
Opposite Direction Pointers
Problems where pointers start from opposite ends and move towards each other.
- 🟩 125. Valid Palindrome [Solution]
- 🟨 189. Rotate Array [Solution]
- 🟨 167. Two Sum II - Input Array Is Sorted [Solution]
Advanced Two Pointers
Sliding Window
A variation of the two pointers technique for substring problems.
Fast and Slow Pointers
Problems involving detecting cycles or finding middle elements.
Multiple Pointers
Problems requiring more than two pointers.
- 🟨 15. 3Sum [Solution]
- 🟨 16. 3Sum Closest [Solution]
Permutation-based
Problems involving permutations solved using two pointers.
Water Container Problems
A specific class of problems involving container capacities.
Complex Processing
Problems requiring more complex logic with two pointers.
Two Pointers in Different Data Structures
String Operations
Applying two pointers technique to string problems.
Problem Difficulty Legend
- 🟩 Easy
- 🟨 Medium
- 🟧 Medium-Hard
- 🟥 Hard
- ⬛ Very Hard
