3 Longest Substring Without Repeating Characters Problem from Leetcode in Javascript

Longest Substring Without Repeating Characters

Problem

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

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.

Given "bbbbb", the answer is "b", with the length of 1.

Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

Difficulty	Related Topics	Similar Questions
Medium	Hash Table Two Pointers String https://leetcode.com/tag/hash-table https://leetcode.com/tag/two-pointers https://leetcode.com/tag/string	Longest Substring with At Most Two Distinct Characters https://leetcode.com/problems/longest-substring-with-at-most-two-distinct-characters

Solution

Here is the solution for the problem in javascript without Regular Expression (Regex)

const longestString = str => {
  obj = {};
  longest = [];
  current = [];
  for (let i=0; i<str.length; i++) {
    if (obj[str[i]] === undefined) {
      obj[str[i]] = 1;
      current.push(str[i]);
    } else {
      if (current.length > longest.length) {
        longest = [...current];
        current = [];
        obj = {};
        obj[str[i]] = 1;
        current.push(str[i]);
      }
    }
  }
  return longest.join('');
}

console.log(longestString('ababcababcababcababcababcababc'));

Output

abc

Run this code here: https://repl.it/@VinitKhandelwal/longest-string-javascript