String Basics

Strings open a lot of Fidelity coding rounds. US new-grad, intern and associate candidates get a short task like the five below, often on a whiteboard or a plain notepad with no compiler. India technical rounds use the same tasks as a warmup before the Java questions. None of them is hard, but a senior engineer reads your code line by line, the way they'd read a pull request, and asks why you picked each type.

Two Java details come up across all five. A String can't change, so any in-place work happens on a char[]. The map also has to fit the answer. A plain HashMap has no order, while a LinkedHashMap or an int[] indexed by character keeps the order that a "first" or "in order" answer needs.

Java is the safe default here, since the follow-ups often turn on details like String immutability or LinkedHashMap order. If the panel lets you call a built-in, use it, and be ready to write the loop by hand when they ask again without it.

FidelityPremium lesson · Coding round

The 5 Fidelity problems are below.

1. 1A Premium questionCoding · Easy · Signature problem
2. 2A Premium questionCoding · Easy · Frequently asked
3. 3A Premium questionCoding · Easy

+ 2 more in this lesson

Each with hints, the follow-up and a tested solution.

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