Given a string, find the length of the **longest substring** without repeating characters.

**Example 1:**

Input:"abcabcbb"Output:3Explanation:The answer is`"abc"`

, with the length of 3.

**Example 2:**

Input:"bbbbb"Output:1Explanation:The answer is`"b"`

, with the length of 1.

**Example 3:**

Input:"pwwkew"Output:3Explanation:The answer is`"wke"`

, with the length of 3. Note that the answer must be asubstring,`"pwke"`

is asubsequenceand not a substring.