3. Longest Substring Without Repeating Characters
Medium

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.
```

 

Constraints:

    0 <= s.length <= 5 * 104
    s consists of English letters, digits, symbols and spaces.