Sliding Window: longest substring with distinct characters

longestSubstringDistinctCharacter.js

const longestSubstringWithDistinctCharacters = str => {
  let windowStart = 0;
  let longestSubstring = 0;
  const hashMap = {};

  // Expand the window
  for (let windowEnd = 0; windowEnd < str.length; windowEnd++) {
    const rightChar = str[windowEnd];

    // if the map already contains the 'rightChar', shrink the window from the beginning
    // so that we have only one occurrence of 'rightChar'
    if (rightChar in hashMap) {
      windowStart = windowEnd;
    } else {
      // insert rightChar into the map
      hashMap[rightChar] = windowEnd;
    }

    // remeber the max length so far
    longestSubstring = Math.max(longestSubstring, windowEnd - windowStart + 1);
  }

  return longestSubstring;
};

longestSubstringWithDistinctCharacters('aabccbb');
longestSubstringWithDistinctCharacters('abbbb');
longestSubstringWithDistinctCharacters('abccde');