Best Time to Buy and Sell Stock — C# Coding Problem
Difficulty: easy | Category: array
Problem Description
You are given an array `prices` where `prices[i]` is the price of a given stock on the `i`th 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`.
Examples
Example 1
Input: prices = [7, 1, 5, 3, 6, 4]
Output: 5
Explanation: Buy on day 2 (price=1), sell on day 5 (price=6). Profit = 6 - 1 = 5.
Example 2
Input: prices = [7, 6, 4, 3, 1]
Output: 0
Explanation: Prices only decrease — no profit possible.