Given a string S, find length of the longest substring with all distinct characters. 

Example 1:

Input:
S = "geeksforgeeks"
Output: 7
Explanation: "eksforg" is the longest 
substring with all distinct characters.

​Example 2:

Input: 
S = "aaa"
Output: 3
Explanation: "a" is the longest substring 
with all distinct characters.

Your Task:
You don't need to read input or print anything. Your task is to complete the function longestSubstrDitinctChars() which takes the string S as input and returns the length of the longest substring with all distinct characters.

Expected Time Complexity: O(|S|).
Expected Auxiliary Space: O(1).

Constraints:
1<=|S|<=10⁵