Algorithm Diary

A personal learning journal for tracking algorithm problem-solving progress. Includes solutions, failed attempts analysis, and a retry list for spaced repetition practice.

📚 What is this?

This repository serves as a structured system for mastering algorithms and data structures through three key components:

• Solutions Diary — Optimal solutions with time/space complexity analysis
• Mistakes Diary — Failed attempts with root cause analysis
• Retry List — Problems to revisit using spaced repetition

📁 Structure

algorithm-diary/
├── retry-list/
│   └── README.md              # Problems to revisit (remove when solved)
├── problems/
│   ├── array/
│   │   └── two-sum/
│   │       ├── solution.md    # Optimal solution + explanation
│   │       └── fails.md       # Failed attempts + analysis
│   ├── linked-list/
│   │   ├── reverse-list/
│   │   └── merge-lists/
│   ├── tree/
│   ├── graph/
│   ├── dynamic-programming/
│   ├── binary-search/
│   └── ...
└── README.md

📝 Solution Template

Each solution.md follows this structure:

# Problem Name

[LeetCode Link](https://leetcode.com/problems/...)

## Solution

\`\`\`python
# Code here
\`\`\`

## Complexity

**Time:** `O(n)` — explanation  
**Space:** `O(n)` — explanation

## Approach

Step-by-step explanation of the solution logic.

❌ Fails Template

Each fails.md documents failed attempts:

# Failed Attempts

## Attempt 1 — TLE
\`\`\`python
# Failed code
\`\`\`
**What went wrong:** Used nested loops O(n²) instead of hashmap O(n)

## Attempt 2 — Wrong Answer
\`\`\`python
# Failed code
\`\`\`
**What went wrong:** Off-by-one error in boundary check

🔄 Retry List

Problems that couldn't be solved within 30 minutes go to retry-list/README.md

Spaced Repetition Schedule:

• First retry: 1-2 days after initial attempt
• Second retry: 1-2 weeks later
• Remove from list when solved confidently

🏷️ Topics

• Array
• String
• Linked List
• Stack / Queue
• Tree / Binary Tree
• Graph
• Hash Table
• Binary Search
• Two Pointers
• Sliding Window
• Dynamic Programming
• Greedy
• Backtracking
• Heap / Priority Queue

🎯 Purpose

1. Track progress — See improvement over time
2. Learn from mistakes — Documenting failures prevents repeating them
3. Build a personal cheatsheet — Quick reference before interviews
4. Spaced repetition — Retry list ensures long-term retention

📄 License

This project is licensed under the MIT License.