Find the minimum number of character changes needed so a word becomes k-periodic.
Given a lowercase word and an integer , make the word k-periodic by changing as few characters as possible.
A word is k-periodic if every character at positions that differ by a multiple of is the same. Equivalently, for each residue class modulo , all characters in those positions must match.
Your task is to compute the minimum number of operations required, where one operation changes a single character to any other lowercase letter.
Input Format
- A string
wordconsisting of lowercase English letters. - An integer
k.
You may assume the inputs describe a valid instance of the problem.
Output Format
- Return the minimum number of single-character changes needed to make
wordk-periodic.
Constraints
1 <= k <= len(word)wordcontains only lowercase English letters- One operation changes exactly one character
Example 1
Input
word = "leetcode", k = 2
Output
4
Explanation
Positions 0,2,4,6 are l,e,c,d and positions 1,3,5,7 are e,t,o,e. In each group, keep the most frequent letter and change the others. The minimum total changes is 4.
Example 2
Input
word = "aaabbb", k = 3
Output
0
Explanation
Positions grouped by modulo 3 are a,b, a,b, a,b. Each group already has matching characters after considering the repeating pattern, so no changes are needed.
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