String Permutations Program

HardPython

Problem

In i2c configuration tooling, a string may represent selectable characters in a payment or cardholder rule. Given a string and an arrangement mode, generate every unique arrangement without returning duplicates caused by repeated characters.

Implement a function that supports two modes:

"permutations": return every distinct arrangement using all characters exactly once.
"combinations": return every distinct non-empty combination of the characters, where character order within a combination is nondecreasing. Each character occurrence may be used at most once, so repeated input characters are treated as a multiset.

Return results in lexicographic order. For combinations, include combinations of every possible length.

Formal Specification

Input: a string s containing lowercase English letters and a string mode, either "permutations" or "combinations".
Output: a list of unique strings sorted lexicographically.
The input string may contain repeated characters.

Constraints

0 <= len(s) <= 9
s contains only lowercase English letters
mode is either "permutations" or "combinations"
Results must contain no duplicates
Results must be sorted lexicographically

Function Signature

def generate_arrangements(s, mode):

Implement a function that supports two modes:

"permutations": return every distinct arrangement using all characters exactly once.
"combinations": return every distinct non-empty combination of the characters, where character order within a combination is nondecreasing. Each character occurrence may be used at most once, so repeated input characters are treated as a multiset.

Return results in lexicographic order. For combinations, include combinations of every possible length.

Formal Specification

Input: a string s containing lowercase English letters and a string mode, either "permutations" or "combinations".
Output: a list of unique strings sorted lexicographically.
The input string may contain repeated characters.