Longest Substring Without Repeating Characters

Given a string `s`, find the length of the **longest** **substring** without duplicate 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. ```   **Constraints:** - `0 <= s.length <= 5 * 104` - `s` consists of English letters, digits, symbols and spaces.