Given a string s, find the length of the longest substring without repeating characters.
A substring is a contiguous non-empty sequence of characters within a string.
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 "pwke" is a subsequence, not a substring.
0 <= s.length <= 5 * 10⁴s consists of English letters, digits, symbols, and spaces.