You are given a string containing only four kinds of characters: ‘Q’, ‘W’, ‘E’, and ‘R’. The string is balanced if each character appears exactly n/4 times, where n is the length of the string. The task is to find the minimum length of a substring that can be replaced to make the string balanced.
You are given an array of integers nums and an integer k. A subarray is considered ’nice’ if it contains exactly k odd numbers. Your task is to return the number of nice subarrays in the given array.
Given a string s, return the maximum number of occurrences of any substring that satisfies the following conditions: The number of unique characters in the substring must be less than or equal to maxLetters, and the substring length must be between minSize and maxSize inclusive.
Given an array of integers arr and two integers k and threshold, return the number of subarrays of size k whose average is greater than or equal to the threshold.
Given a string s consisting only of characters ‘a’, ‘b’, and ‘c’, your task is to find the number of substrings that contain at least one occurrence of each of the characters ‘a’, ‘b’, and ‘c’.
You are given an array cardPoints representing the points of cards arranged in a row. In each step, you can pick the first or the last card from the row. Your goal is to pick exactly k cards and maximize the sum of the points of the cards you select.