Leetcode3 longest substring whitout repeat characters

Evaluate the length of the longest non-duplicate substring in the string, for example, "abcabcbb". The longest non-duplicate substring is "ABC" and the length is 3. Because there are no duplicates required, we want to use hashmap to store them, because the key values of hashmap cannot be repeated. The character to be saved is used as the key, and the subscript of the character in the string is used as the value. If the map already contains this character, the character and all the characters before this character are deleted, and then store the data. For example, if the string is "abcbd", if ABC has been saved, and B is saved now, AB is deleted and saved to (B, 3). Max is the value that contains the maximum number of characters in map.

Leetcode3 longest substring whitout repeat characters