Substrings of Size Three with Distinct Characters
The problem is asking us to find the number of substrings of length 3 from the given string that have all distinct characters.
We can use a sliding window approach to solve this problem.
Here is a Python solution:


We loop over the string from index 0 to len(s)  2
. For each index i
, we extract a substring of length 3. We then check whether all characters in the substring are unique by converting the substring to a set and checking if the length of the set is 3 (since a set in Python only contains unique elements). If all characters are unique, we increment the count.
This solution works because it checks all possible substrings of length 3 in the string, and for each substring, it checks whether all characters are unique, which is exactly what the problem asks us to do. The time complexity is O(n), where n is the length of the string.
Q&A
Do this question after doing the above question: “Longest Substring Without Repeating Characters”