readme.md

Challenge: Are all characters unique?

Instructions

Write a function called areAllCharactersUnique that takes in a string and returns true or false depending on whether all characters in the string are unique (i.e., no character is repeated).

Function Signature

/**
 * Returns true if all characters in a string are unique.
 * @param {string} str - The string to check.
 * @returns {boolean} - Whether all characters in the string are unique.
 */
function areAllCharactersUnique(str: string): boolean;

Examples

areAllCharactersUnique('abcdefg'); // true
areAllCharactersUnique('abcdefgA'); // true
areAllCharactersUnique('programming'); // false
areAllCharactersUnique(''); // true
areAllCharactersUnique('a'); // true

Constraints

• It should be case sensitive, so a and A are considered different characters
• An empty string should return true by default

Hints

• You can use a for loop to iterate through the string and check if the current character is in the set or object.

Solutions

Click For Solution 1

Using a Set:

function areAllCharactersUnique(str) {
  const charSet = new Set();

  for (let i = 0; i < str.length; i++) {
    const char = str[i];
    if (charSet.has(char)) {
      return false;
    }
    charSet.add(char);
  }

  return true;
}

Explanation

-Initialize a new Set to keep track of the characters we've seen so far.

• Iterate through the string and check if the current character is in the set. If it is, we return false because it means we've seen the character before. If it isn't, we add it to the set.
• If we make it through the entire string without returning false, we return true because it means we haven't seen any characters more than once.

Click For Solution 2

Using an object:

function areAllCharactersUnique(str) {
  const charCount = {};

  for (let i = 0; i < str.length; i++) {
    const char = str[i];
    if (charCount[char]) {
      return false;
    }
    charCount[char] = true;
  }

  return true;
}

Explanation

This solution is similar except we use an object instead of a Set to keep track of the characters we've seen so far.

Then we iterate through the string and check if the current character is in the object. If it is, we return false because it means we've seen the character before. If it isn't, we add it to the object.

If we make it through the entire string without returning false, we return true because it means we haven't seen any characters more than once.

Test Cases

test('Unique Characters in a String', () => {
  expect(areAllCharactersUnique('abcdefg')).toBe(true);
  expect(areAllCharactersUnique('abcdefgA')).toBe(true);
  expect(areAllCharactersUnique('programming')).toBe(false);
  expect(areAllCharactersUnique('')).toBe(true);
  expect(areAllCharactersUnique('a')).toBe(true);
});