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DSA learning path

Arrays & Strings

Traversal, two pointers, sliding window, prefix sums.

Start with Two Sum

Problems in this path

  1. Two Sum
    Easy · Hash Map
    Open
  2. Pair Sum in a Sorted Array
    Easy · Two Pointers
    Open
  3. Maximum Sum of k Consecutive Values
    Easy · Sliding Window
    Open
  4. Range Sum Queries
    Easy · Prefix Sum
    Open
  5. Valid Palindrome
    Easy · Two Pointers
    Open
  6. Longest Substring Without Repeats
    Medium · Sliding Window
    Open
  7. Maximum Subarray
    Medium · Kadane's Algorithm
    Open
  8. Trapping Rain Water
    Hard · Two Pointers
    Open
  9. Product Except Self
    Medium · Prefix and Suffix Products
    Open
  10. Majority Element
    Easy · Boyer-Moore Voting
    Open

Read first

Big-O and Complexity

How to describe how fast code grows as its input grows, and why O(n log n) beats O(n²) long before your computer runs out of patience.

12 min read

Arrays and Dynamic Arrays

Why reading arr[i] is instant, why inserting at the front is slow, and how lists that grow (Python list, ArrayList, vector) work underneath.

14 min read

Prefix Sums and Difference Arrays

Precompute cumulative information for constant-time range queries, then reverse the idea to apply many range updates efficiently.

14 min read