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LeetCode, Agents, or Fundamentals. What Should a Junior Practice in 2026?

5 min read
  • learning
  • junior-developer
  • interview
  • ai

You have three tabs open.

One is a 150-problem grind. One is Claude Code chewing through a side project. One is a thread that says "skip LeetCode, companies want AI-native now."

All three sound true. None of them tell you what to do this week.

That is not a motivation problem. The map changed and nobody handed you a new one. You can finish tickets with an agent and still have no idea whether you are closer to hireable.

You are not picking a camp. You are picking a mix.

In 2026 junior hiring is not one game. It is three, often in the same loop.

Game What it scores Where it still shows up
LeetCode-style Pattern recall, clean implementation, timed pressure Some Big Tech loops, older take-homes, "prove you can code" screens
Agent fluency Decompose, prompt, verify, narrate, catch a bad diff AI-allowed rounds, startups, "build this small feature with your tools"
Fundamentals Explain a loop, debug a stack trace, name an edge case without a sidebar Almost every live conversation, including the ones that let you use Claude

Tutorials and Twitter pick a winner. Interviewers do not. They mix rooms. A company can ban assistants on Tuesday and drop you into Gemini-in-the-editor on Thursday.

If you only grind mediums, you freeze when the task is "read this agent diff." If you only vibe-code, you freeze when the assistant is off. If you only watch fundamentals videos, you never get reps under mild pressure.

The junior who gets the offer is rarely the one who picked the loudest camp. It is the one who can transfer: same idea, less help, next time.

What each camp is actually for

LeetCode is a sport, not a personality

It still matters where they still play it. It is a weak default for everyone else.

Do not use it as proof you grew. Passing 200 mediums and blanking on "what happens if this field is null?" is a known outcome. Use a small, honest set if your target companies score that sport. Do not let it eat the week because it has a progress bar.

Agents are the job. Verification is the skill.

Claude Code, Cursor Agent, Copilot agent mode, Windsurf: these are how tickets move in 2026. Fluency is not secret prompt paste.

Fluency looks like:

  • a short plan before a wide generate
  • reading the diff like you did not write it (because you did not)
  • a test or a failing case the agent did not volunteer
  • a sentence for why this approach, out loud

"I shipped eight apps with v0 / Lovable / Replit Agent" is a portfolio. It is not a story until you can talk about one decision you made and one mistake you caught.

Fundamentals are the transfer layer

Not "never use AI." The bits that survive every format:

  • say the input and output before you touch a tool
  • form a debug hypothesis before you paste a stack trace
  • explain a working function without scrolling
  • change one constraint (sorted → unsorted, exists → count) and predict what breaks

That is what "walk me through it" is asking for, with or without a model in the pane.

A week that is not a second job

You do not need heroic hours. You need a split you can repeat.

  • 3 short sessions: closed-book or hint-only on a tiny problem (string, array, a small bug). Attempt first. No dumped solution.
  • 2 sessions: ship something with your usual agent, then defend it: close the chat, narrate the diff, mark one line you cannot explain.
  • 1 session: a neighbour problem. Same idea as earlier in the week, different constraint, less help than last time.

If session six is not easier than session one on that class of problem, you practised output. You did not practise independence.

Keep a one-line log: problem, help used (none / hint / dump), could I explain it tomorrow? The log is the compass. A new stack every weekend is not.

How you know the mix is working

Skip "I feel productive." Watch these instead:

  • You can restate last week's change without opening the PR.
  • You debug with a guess before a prompt.
  • The same family of problem needs a shallower hint than last week.

Tools will keep getting faster. Your job is to stay the person who can still think when the tool is missing, wrong, or watching you.

Where Prepzio fits

Prepzio exists because this mix is hard to hold in your head. It does not ban AI and it does not replace LeetCode.

Short Socratic sessions. Hint ladders instead of answer dumps. Rubric feedback on reasoning. An Independence Score (and levels L1–L5) so "am I getting better?" is a trend, not a mood.

If you want a seven-day loop aimed at weak spots instead of another generic grind, that is the product.

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