3137. Minimum Number of Operations to Make Word K-Periodic

You are given a string word of size n, and an integer k such that k divides n.

In one operation, you can pick any two indices i and j, that are divisible by k, then replace the substring of length k starting at i with the substring of length k starting at j. That is, replace the substring word[i..i + k - 1] with the substring word[j..j + k - 1].

Return the minimum number of operations required to make word k-periodic.

We say that word is k-periodic if there is some string s of length k such that word can be obtained by concatenating s an arbitrary number of times. For example, if word == “ababab”, then word is 2-periodic for s = "ab".

3136. Valid Word

A word is considered valid if:

• It contains a minimum of 3 characters.
• It consists of the digits 0-9, and the uppercase and lowercase English letters. (Not necessary to have all of them.)
• It includes at least one vowel.
• It includes at least one consonant.

You are given a string word.

Return true if word is valid, otherwise, return false.

Notes:

• 'a', 'e', 'i', 'o', 'u', and their uppercases are vowels.
• A consonant is an English letter that is not a vowel.

think-cell Round 1 D2. Sum over all Substrings (Hard Version)

think-cell Round 1 D1. Sum over all Substrings (Easy Version)

think-cell Round 1 C. Lexicographically Largest

Codeforces Round 924 (Div. 2) C. Physical Education Lesson

Educational Codeforces Round 162 (Rated for Div. 2) D. Slimes

3125. Maximum Number That Makes Result of Bitwise AND Zero

Given an integer n, return the maximum integer x such that x <= n, and the bitwise AND of all the numbers in the range [x, n] is 0.

3135. Equalize Strings by Adding or Removing Characters at Ends

Given two strings initial and target, your task is to modify initial by performing a series of operations to make it equal to target.

In one operation, you can add or remove one character only at the beginning or the end of the string initial.

Return the minimum number of operations required to transform initial into target.

2000. Reverse Prefix of Word

Given a 0-indexed string word and a character ch, reverse the segment of word that starts at index 0 and ends at the index of the first occurrence of ch (inclusive). If the character ch does not exist in word, do nothing.

• For example, if word = "abcdefd" and ch = "d", then you should reverse the segment that starts at 0 and ends at 3 (inclusive). The resulting string will be "dcbaefd".

Return the resulting string.