Acronym Builder - FreeCodeCamp #29 Daily Challenge

Acronym Builder

1. Problem Statement

Given a string of one or more words, return the acronym following these rules:

• The acronym is the first letter of each word (uppercase), unless the word is in the ignore list and not the first word.
• Ignore words (except if first): a, for, an, and, by, of.
• The order of the letters matches the original order.
• No spaces in the result.

2. Test Cases

3. Solution & Code

Strategy:

1. Split the string into words.
2. Define a Set with the ignore words.
3. Iterate each word:

• If it’s the first word, always take it.
• If not in the ignore set, take it.
• Add the first letter (uppercase) to the acronym.

4. Join the letters and return the result.

function buildAcronym(str) {
  const ignore = new Set(['a', 'for', 'an', 'and', 'by', 'of'])
  return str
    .split(/\s+/)
    .filter(Boolean)
    .reduce((acronym, word, idx) => {
      if (idx === 0 || !ignore.has(word.toLowerCase())) {
        return acronym + word[0].toUpperCase()
      }
      return acronym
    }, '')
}

Flowchart

flowchart TD
A["Start"] --> B["Split into words"]
B --> C["Iterate words"]
C --> D{"Is it first or not in ignore?"}
D -- Yes --> E["Add first letter (uppercase)"]
D -- No --> F["Skip"]
E --> G["Next word"]
F --> G
G --> H{"End?"}
H -- No --> C
H -- Yes --> I["Join letters and return"]

4. Complexity

• Time: $O(n)$, one pass through the words.
• Space: $O(n)$, for the words array and ignore set.

5. Edge Cases

• Empty string → empty acronym
• All words ignored → only the first is taken
• Mixed case: normalized for comparison
• Multiple spaces: filtered

6. Reflections

• Using a Set for ignore words is efficient and clear.
• The algorithm is robust and easy to adapt (e.g., to ignore more words).
• Can be improved by removing punctuation or allowing a configurable ignore list.

7. Resources

• String.prototype.split() on MDN
• Set in JavaScript