3675 - Minimum Operations to Transform String.

Medium

You are given a string s consisting only of lowercase English letters.

You can perform the following operation any number of times (including zero):

• Choose any character c in the string and replace every occurrence of c with the next lowercase letter in the English alphabet.

Return the minimum number of operations required to transform s into a string consisting of only 'a' characters.

Note: Consider the alphabet as circular, thus 'a' comes after 'z'.

Example 1:

Input: s = "yz"

Output: 2

Explanation:

• Change 'y' to 'z' to get "zz".

• Change 'z' to 'a' to get "aa".

• Thus, the answer is 2.

Example 2:

Input: s = "a"

Output: 0

Explanation:

• The string "a" only consists of 'a' characters. Thus, the answer is 0.

Constraints:

• <code>1 <= s.length <= 5 * 10⁵</code>

• s consists only of lowercase English letters.