Longest Substring Without Repeating Characters

Description

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

 

Example 1:

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

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 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.

Example 4:

Input: s = ""
Output: 0

 

Constraints:

• 0 <= s.length <= 5 * 104
• s consists of English letters, digits, symbols and spaces.

Solution(javascript)

const lengthOfLongestSubstring = (s = '') => {
  const map = {}
  let max = 0
  let left = -1
  for (let i = 0; i < s.length; i++) {
    if (map[s[i]] !== undefined) {
      left = Math.max(left, map[s[i]])
      max = Math.max(i - left, max)
    } else {
      max = Math.max(i - left, max)
    }
    map[s[i]] = i
  }
  return max
}