Question 3 Longest Substring

The description of the question is in the following link.

The idea is really clear: For the longest substring, different from the longest subsequence, they must be continuous, hence if for the first time we meet a repeated character, we shall abandon all the character before and included the repeated one, because for any string starting before the repeated character, there will always be a repetition in the string. For each time, we take the maximum between the max we have already had and the maximum of sub string we have now.