main.go

// Source: https://leetcode.com/problems/best-time-to-buy-and-sell-stock
// Title: Best Time to Buy and Sell Stock
// Difficulty: Easy
// Author: Mu Yang <http://muyang.pro>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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 <= 10^5
//   0 <= prices[i] <= 10^4
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package main

func maxProfit(prices []int) int {
	profit := 0
	minPrice := prices[0]

	for _, price := range prices {
		if price < minPrice {
			minPrice = price
		} else {
			profit = _max(profit, price-minPrice)
		}
	}

	return profit
}

func _max(a, b int) int {
	if a > b {
		return a
	}
	return b
}