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# 3. 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.