You're given a directed graph. Determine the minimum number of edges you need to reverse so that every node becomes reachable from node 0.

Find two numbers in a given array that add up to a specific target value, and return their indices. Essentially, you need to efficiently locate the pair that satisfies the sum requirement.

Determine if a given word is considered valid based on a specific set of rules or constraints. The goal is to check if the input string adheres to the specified validation criteria.