I spent two weeks solving identical problems in Python, Java, Go and C++ to see whether the language actually mattered. It did, just not in the way I expected.
From two weeks of side-by-side practice · Updated September 2026 · 8 min read
The short answer: interview in the language you think in, not the one you think looks impressive. Python is the shortest to write and the easiest to explain, which matters on a whiteboard. Java and C++ are fine if they're what you use daily. The worst choice is switching languages two weeks before interviews, which is what I nearly did.
Line counts are from my own solutions, written in a normal interview style. Yours will vary.
Why I tried this at all
A senior told me Java was "slowing me down".
I've written Java at work for three years. A friend who'd just been through a round of interviews told me to switch to Python, because "nobody has time to type HashMap in an interview". It sounded plausible. It also sounded like the kind of advice that costs you two weeks.
So instead of switching, I tested it. Same problems, four languages, two weeks. I used Phantom Code AIhttps://www.phantomcodeai.com/
to check each solution afterwards, because it lets you pick the output language per session, which made side-by-side comparison easy. The rest I did on paper.
What the line counts showed
Less difference than I expected.
Python is shortest, clearly. But look at the spread: six lines against ten. In a 45-minute interview, four extra lines are not what decides the outcome. What decided my outcomes was how quickly I could reason, and that turned out to depend on something else.
Typing speed was never my bottleneck. Remembering syntax under pressure was.
What actually changed between languages
The part that surprised me.
Where Python helped
Fewer lines to explain on a shared screen
Built-in structures: dict, set, heapq, deque
Slicing and enumerate make edge cases shorter
Easier to read aloud to an interviewer
Where Python hurt me
I kept forgetting heapq is a min-heap
I second-guessed default argument behaviour
My explanations got vaguer, not clearer
Everything took longer in week one
The second column is the one nobody mentions. In Java I never thought about syntax; my hands knew it. In Python I spent the first week pausing to remember whether it was sorted() or .sort(). Those pauses feel huge in an interview.
How I'd decide, in four questions
A simple way to choose.
I went back to Java. My solutions were longer but my explanations were calmer, and interviewers kept asking about my reasoning, never my line count. I still use Python to sketch ideas quickly before writing the real thing.
One more thing that applies to every language: none of this belongs in the live interview itself. AI tools are for practice; employers and assessment platforms treat hidden assistance during a real interview as cheating.
Common questions
Short answers.
What's the best language for coding interviews?
Is Java bad for interviews?
Should I switch to Python?
Does the company's stack matter?
The honest conclusion
The language advice I got was well meant and mostly wrong for me. The best interview language is the one where your hands stop thinking about syntax and your head can focus on the problem.
Test it before you switch. Two weeks of side-by-side practice saved me from a mistake that would have cost the same two weeks right before my interviews.
— Still writing HashMap, happily
Which language do you interview in?
And did you ever regret it?
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