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.

You're given daily stock prices. Find the maximum profit you can make by buying and selling the stock once. You must buy before you sell.

Rearrange the characters in a given string such that no two adjacent characters are the same. If such an arrangement is possible, return it; otherwise, return an empty string.