You are given two gene strings, startGene and endGene, both consisting of 8 characters. You also have a gene bank of valid gene strings that can be mutated into one another. A mutation is defined as changing one character at a time, and the mutated gene string must exist in the gene bank. Your task is to determine the minimum number of mutations needed to transform startGene into endGene. If transformation is impossible, return -1.
You are given two strings, s and p. Return the list of start indices of all the anagrams of string p in string s. An anagram of p is a rearrangement of the characters of p, and the start indices should be returned in any order.
Given an array of characters, compress it by replacing consecutive repeating characters with the character followed by the count of repetitions. If the character repeats only once, just include the character. The result should modify the input array and return the new length of the array.
Design an algorithm to serialize and deserialize a binary search tree (BST). Serialization is converting the tree to a string format, while deserialization reconstructs the tree from this string. The goal is to ensure that the BST can be serialized to a compact string and can be accurately deserialized back into the original tree structure.
Given a string, sort its characters based on their frequency of occurrence in descending order. If multiple solutions are possible, any valid answer is acceptable. The frequency of each character refers to how many times it appears in the string.
