3. Longest Substring Without Repeating Characters

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

Given a string s, find the length of the longest substring without repeating characters.

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

note

This question can be solved by sliding window.

• When should I move the left pointer?
• When should I move the right pointer?

Solution:

/**
 * @param {string} s
 * @return {number}
 */
var lengthOfLongestSubstring = function (s) {
  let left = 0;
  let right = 0;
  const set = new Set();
  let result = 0;
  while (right < s.length) {
    while (set.has(s.charAt(right))) {
      set.delete(s.charAt(left)); // move left boundary
      left++;
    }

    set.add(s.charAt(right));
    right++;
    result = Math.max(result, set.size);
  }

  return result;
};

console.log(lengthOfLongestSubstring("pwwkew")); // 3
console.log(lengthOfLongestSubstring("abcabcbb")); // 3