Minimum changes to make all substrings distinct

source:https://practice.geeksforgeeks.org/problems/minimum-changes-to-make-all-substrings-distinct/0

Given a string s, find the minimum number of changes required to it so that all substrings of the string become distinct.

Note: length of string is atmost 26.

Input:
The first line contains an integer T, number of test cases. For each testcase there is only one line containing s atmost 26 characters.

Output:
For each testcase in new line, print the minimum number of changes to the string.

Constraints:
1 <= T <= 100
1 <= |s| <= 26

Example:
Input
3
aab
aebaecedabbee
ab

Output
1
8
0

Explanation
Testcase 1: If we change one instance of ‘a’ to any character from ‘c’ to ‘z’, we get all distinct substrings.
Testcase 2: We need to change 2 a’s, 2 b’s and 4 e’s to get distinct substrings.
Testcase 3: As no change is required hence 0.

Answer:

t=int(input())
for x in range(t):
s = input()
a = list(s)
b = []
for i in a:
if i in b:
pass
else:
b.append(i)
print(len(a) — len(b))