1. You are given an array prices where prices[i] is the price of a given stock on the ith day. You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock. Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.
2. How do you plan a recruitment drive?
3. Remove Duplicates from String Problem Statement You are provided a string STR of length N, consisting solely of lowercase English letters. Your task is to remove all duplicate occurrences of characters in the string. Example: Input: abcadeecfb Output: abcdef Explanation: After removing duplicates, the string becomes abcdef. Constraints: 1 ≤ N <= 4*10^5 Time Limit: 1 sec