Explaining Algorithms in Plain English

Direct Answer

Use a three-part structure: state what the algorithm does at a high level in one sentence, explain the key steps in order using simple everyday language, and mention the data structure that makes it work. Avoid technical jargon in the English explanation — save the jargon for when you write the code.

Code Example

// Interviewer: Find the first non-repeating character in a string

// Plain-English explanation:
// "The algorithm does this: finds the first character that appears only once."
// "Step 1: I walk through the string once and count how many times each character appears."
// "Step 2: I walk through the string a second time and return the first character with count of 1."
// "The data structure I need is a HashMap to store character counts."
// "Does that make sense? Should I code it?"

public Optional<Character> firstNonRepeating(String input) {
    // Now coding the English explanation:
    var counts = new HashMap<Character, Integer>();
    
    // Step 1: Count occurrences
    for (var ch : input.toCharArray()) {
        counts.put(ch, counts.getOrDefault(ch, 0) + 1);
    }
    
    // Step 2: Find first with count 1
    for (var ch : input.toCharArray()) {
        if (counts.get(ch) == 1) {
            return Optional.of(ch);
        }
    }
    
    return Optional.empty();
}

Common Mistakes & Pitfalls

• Skipping Explanation Entirely: Jumping straight into code without verbalizing the approach — if you misunderstood the problem, you waste 10 minutes coding the wrong solution.
• Using Jargon in English: Saying 'I'll use a memoized recursive approach with a DP table' instead of 'I'll solve smaller subproblems and remember their answers' — the interviewer can't tell if you truly understand or are just repeating terms.
• Vague High-Level Description: Saying 'I'll iterate through the array' without explaining what you do on each iteration or what you're looking for.
• No Check-In: Explaining your approach then immediately starting to code without asking 'Does this make sense?' — you miss the chance for early feedback.
• Over-Explaining Edge Cases in English: Spending two minutes explaining how you handle nulls and empty strings before explaining the core algorithm — explain the happy path first, edge cases come later.