Study Summary — April 28, 2026

LeetCode — Minimum Path Sum (Medium)

Key Concepts

• 2D bottom-up DP: dp[i][j] = grid[i][j] + min(dp[i-1][j], dp[i][j-1]). The optimal path to any cell only depends on the cell directly above and the cell directly to the left.

• Boundary handling: The first row only has the cell to the left as a predecessor; the first column only has the cell above. Initialize them with prefix sums of the grid's first row/column.

• Space optimization: Because each row only depends on the previous row, you can compress the DP to a single 1D array of size n, reducing space from O(m·n) to O(n).

• In-place variant: If you're allowed to mutate the input grid, you can overwrite grid[i][j] with the running minimum sum and use O(1) extra space.

• Approach hint: Walk the grid row by row, left to right. For each cell, add grid[i][j] to the smaller of the two valid predecessors. Return dp[m-1][n-1].

Professional Programming — Interviewing

• Coding Interview University — a complete CS study plan to become a software engineer.

• I spent 3 months applying to jobs after a coding bootcamp. Here's what I learned.

• How to ask good questions — Julia Evans

Key Concepts

• Treat the interview as a two-way evaluation. You're assessing whether the team, codebase, and growth path actually match what you want — not just performing for them.

• Practice pattern recognition over memorization. Most coding-interview problems are variations on a small number of patterns (two pointers, sliding window, BFS/DFS, DP on grids, intervals, heaps). Drilling patterns generalizes; memorizing solutions does not.

• Talk through your thinking out loud. Interviewers grade on how you think, not just whether you reach the optimal answer. State assumptions, name the data structure you're reaching for, and explain trade-offs as you code.

• Ask sharp clarifying questions before coding. Confirm input bounds, edge cases (empty input, duplicates, negatives), and whether you can mutate the input. This signals seniority and saves you from rewrites.

• Reflect after every interview. Capture what went well, the moments you stalled, and one concrete thing to drill before the next loop. The fastest interview improvement comes from this feedback cycle, not from grinding more problems.

Claude Code Docs — Subagents

Key Concepts

• What a subagent is: A specialized assistant with its own context window, system prompt, and (optionally) restricted tool list. It runs a side task without flooding the main conversation with logs or search results.

• Why use them: Preserve main-thread context, enforce constraints (e.g. a code-reviewer that only has read tools), reuse configurations across projects, route cheap tasks to faster/cheaper models, and specialize behavior with focused prompts.

• How to define one: Author a Markdown file with YAML frontmatter — frontmatter configures the agent (name, description, allowed tools, model), and the body becomes its system prompt. Store project-level agents in .claude/agents/ and user-level agents in ~/.claude/agents/.

• How to invoke: Use natural language ("Use the test-runner subagent to fix failing tests"), @-mention the agent by name, or call it via the Agent tool from the SDK. Claude Code also ships built-ins like Explore, Plan, and general-purpose.

• Design tip: Write the description like a routing hint — start with the trigger conditions ("Use proactively after writing code to review for bugs and security issues"). Good descriptions get auto-delegated; vague ones don't.

ByteByteGo — Life is Short, Use Dev Tools

Key Concepts

• A tuned local environment is a force multiplier. Editors and IDEs (VS Code, IntelliJ, Vim, PyCharm, Jupyter) eliminate friction on the operations you do hundreds of times a day. The compounding return justifies investing in shortcuts, snippets, and config.

• AI assistants belong in the toolchain now. GitHub Copilot, Claude Code, ChatGPT, Tabnine, and local models like Ollama collapse the gap between intent and code. Treat them as pair programmers, not autocomplete.

• Make ideas visible with the right diagram tool. Excalidraw and Mermaid are great for whiteboard-style sketches; PlantUML, draw.io, Visio, and Miro scale for architecture diagrams and team workshops. Visual artifacts beat long Slack threads.

• Bake quality and security into your workflow. Linters and test runners (ESLint, Jest, SonarQube), plus security tools (1Password/LastPass for secrets, Snyk and OWASP for dependency and app scanning), catch issues before they ship rather than after.

• Pick a hosting stack that matches your stage. Cloudflare, Fly, Heroku, and Digital Ocean optimize for speed of iteration; AWS and GCP optimize for scale. Don't pay the AWS complexity tax for a side project.