Short Problem Definition:
Amanda has a string of lowercase letters that she wants to copy to a new string. She can perform the following operations with the given costs. She can perform them any number of times to construct a new string p:
 Append a character to the end of string p at a cost of 1 dollar.
 Choose any substring of p and append it to the end of at no charge.
Link
Complexity:
time complexity is O(N)
space complexity is O(N)
Execution:
The solution sounds too easy, but it is still very simple. A substring of length 1 is still a substring. Each character in the final string needs to be copied once for 1$. Each other occurrence of that string can be copied for 0$. Aka just count the number of distinct letters in the expected string.
Solution:
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def stringConstruction(s): return len ( set (s)) 