Given a string s, find the length of the longest substring without repeating characters.
Example 1:
1 2 3
Input: s = "abcabcbb" Output: 3 Explanation: The answer is "abc", with the length of 3.
Example 2:
1 2 3
Input: s = "bbbbb" Output: 1 Explanation: The answer is "b", with the length of 1.
Example 3:
1 2 3 4
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.