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 = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.
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.
Input: s = "abcdeaf"
Output: 6
Explanation: The answer is "bcdeaf", with the length of 6.
Input: s = "abcdcbazzf"
Output: 5
Input: s = "abcdef"
Output: 6
0 <= s.length <= 5 * 104sconsists of English letters, digits, symbols and spaces.