Coding Challenge:: firstNonRepeatedCharacter

challenge.js

/*
Solution has been optimized for 0(n) speed

indexOf has a time complexity of O(n), which means that the loop
could potentially have a time complexity of O(n^2) in the worst case,
where n is the length of the input string.

To avoid this performance issue, we use a plain JavaScript object
instead of a Map to store the character count, and use a separate loop to
find the first non-repeated character
*/

function firstNonRepeated(s) {
  const charCount = new Map();
  let nonRepeatedChar = "";

  for (const char of s) {
    charCount.set(char, (charCount.get(char) || 0) + 1);
  }

  for (const char of s) {
    if (charCount.get(char) === 1) {
      nonRepeatedChar = char;
      break;
    }
  }

  return nonRepeatedChar;
}

// Test the function with the provided examples
console.log(firstNonRepeated("hello")); // Output: "h"
console.log(firstNonRepeated("aabcc")); // Output: "b"
console.log(firstNonRepeated("aabbcc")); // Output: ""