How should I practice Minimum Changes for Palindromic Blocks?

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Problem · String

Minimum Changes for Palindromic Blocks

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● Easy

CitadelINTERNOA

Problem statement

You are given a lowercase string password and a positive integer k. The string length is divisible by k, so it is partitioned into consecutive, non-overlapping blocks of exactly k characters.

Change as few characters as possible so that every block is a palindrome. Blocks are independent and do not need to become equal to one another. Return the minimum number of changed positions.

Function

minChangesForPalindromicBlocks(password: String, k: int) → int

Examples

Example 1

password = "abcaabba"k = 4return = 1

The blocks are abca and abba. The second is already palindromic; changing either b or c in the first block is sufficient.

Example 2

password = "abcdef"k = 3return = 2

The blocks abc and def each have one mismatched mirrored pair, so each needs one change.

Example 3

password = "aaaa"k = 1return = 0

Every one-character block is already a palindrome.

Constraints

1 <= password.length <= 200000
1 <= k <= password.length
password.length % k == 0
password contains only lowercase English letters.