public class Solution
extends Object
121 - Best Time to Buy and Sell Stock\.
Easy
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`.
**Example 1:**
**Input:** prices = [7,1,5,3,6,4]
**Output:** 5
**Explanation:** Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5. Note that buying on day 2 and selling on day 1 is not allowed because you must buy before you sell.
**Example 2:**
**Input:** prices = [7,6,4,3,1]
**Output:** 0
**Explanation:** In this case, no transactions are done and the max profit = 0.
**Constraints:**
* 1 <= prices.length <= 105
* 0 <= prices[i] <= 104