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Challenge: Word Frequency Counter using HashTable

Instructions

Write a function called wordInstanceCounter that takes a string and a word as input and returns the number of instances of that word in the string. This function should count the occurrences of the specified word, ignoring case and excluding punctuation.

Function Signature

/**
 * Returns the number of instances of the specified word in the input string.
 * @param {string} str - The input string containing words.
 * @param {string} word - The word to count instances of.
 * @returns {number} - The number of instances of the specified word.
 */
function wordInstanceCounter(str: string, word: string): number

Examples

console.log(
  wordInstanceCounter('The quick brown fox jumps over the lazy dog.', 'the')
); // Output: 2
console.log(
  wordInstanceCounter(
    'Lorem ipsum dolor sit amet, consectetur adipiscing elit.',
    'ipsum'
  )
); // Output: 1
console.log(wordInstanceCounter('Hello, world!', 'hello')); // Output: 1
console.log(wordInstanceCounter('Hello, Hello, Hello!', 'hello')); // Output: 3

Constraints

• The input string will only contain letters, spaces, and punctuation marks.

Hints

• You can use a HashTable to store the word frequencies, where the word is the key, and the count is the value. Loop through each word, update the count in the HashTable, and return the count of the specified word.

Solution

Click For Solution

function wordInstanceCounter(str, word) {
  const words = str.toLowerCase().split(/\W+/);
  const wordFrequency = new HashTable();
  const targetWord = word.toLowerCase();
  let count = 0;

  for (const currentWord of words) {
    if (currentWord === '') continue;

    if (wordFrequency.has(currentWord)) {
      wordFrequency.set(currentWord, wordFrequency.get(currentWord) + 1);
    } else {
      wordFrequency.set(currentWord, 1);
    }

    if (currentWord === targetWord) {
      count = wordFrequency.get(currentWord);
    }
  }

  return count;
}

Test Cases

test('Counting instances of a word in a string', () => {
  expect(
    wordInstanceCounter('The quick brown fox jumps over the lazy dog.', 'the')
  ).toBe(2);
  expect(
    wordInstanceCounter(
      'Lorem ipsum dolor sit amet, consectetur adipiscing elit.',
      'ipsum'
    )
  ).toBe(1);
  expect(wordInstanceCounter('Hello, world!', 'hello')).toBe(1);
  expect(wordInstanceCounter('Hello, Hello, Hello!', 'hello')).toBe(3);
});