🟡 Longest Substring Without Repeating Characters

<aside> 💡 Sliding window, move right if hashmap doesn’t have letter, move left and delete if hashmap has letter.

</aside>

https://leetcode.com/problems/longest-substring-without-repeating-characters/

function lengthOfLongestSubstring(string) {

  // ...

  while (right < string.length) {

    const currentLetter = string[right];
    const leftLetter = string[left];

    if (!map[currentLetter]) {

      map[currentLetter] = 'literally anything';
      right++;

    } else {

      left++;
      delete map[leftLetter];

    }

    longest = Math.max(longest, right - left);

  }

  return longest;
}

• Solution

🟢 Valid Anagram

<aside> 💡 First loop creates hashmap of letter occurrences. Second decreases the number of occurrences or deletes the letter from hashmap. Return true if hashmap is empty.

</aside>

https://leetcode.com/problems/valid-anagram/

function isAnagram(word1, word2) {

  if (word1.length !== word2.length) {
    return false;
  }

  const map = {};

  for (let letter of word1) {
    if (!map[letter]) {
      map[letter] = 1;
    } else {
      map[letter]++;
    }
  }

  for (let letter of word2) {
    map[letter]--;

    if (map[letter] === 0) {
      delete map[letter];
    }
  }

  return Object.keys(map).length === 0

}

🟡 Longest Repeating Character Replacement

<aside> 💡 When number changes is 2, the string AAABCD has longest substring CCCABD → CCCCCD is 5 characters long (length of window - max occured character = number of possible changes)

</aside>