Best Time to Buy and Sell Stock

Introduction

Given an array of daily stock prices, determine the maximum profit achievable through a series of transactions. You can buy and sell on the same day, but can only hold one share at a time. The goal is to devise a strategy that maximizes profit based on price fluctuations.

Prompt

You are given an integer array of prices where prices[i] is the price of a given stock on the ith day.

On each day, you may decide to buy and/or sell the stock. You can only hold at most one share of the stock at any time. However, you can buy it then immediately sell it on the same day.

Find and return the maximum profit you can achieve.

Example 1:

Input: prices = [7,1,5,3,6,4]
Output: 7
Explanation: Buy on day 2 (price = 1) and sell on day 3 (price = 5)
, profit = 5-1 = 4.
Then buy on day 4 (price = 3) and sell on day 5 (price = 6),
profit = 6-3 = 3.
Total profit is 4 + 3 = 7.

Example 2:

Input: prices = [1,2,3,4,5]
Output: 4
Explanation: Buy on day 1 (price = 1) and sell on day 5 
(price = 5), profit = 5-1 = 4.
Total profit is 4.

Example 3:

Input: prices = [7,6,4,3,1]
Output: 0
Explanation: There is no way to make a positive profit, 
so we never buy the stock to achieve the maximum profit of 0.

Optimized Approach

const maxProfit = function (prices) {
  let total = 0;

  for (let i = 1; i < prices.length; i++) {
    if (prices[i] > prices[i - 1]) {
      total += prices[i] - prices[i - 1];
    }
  }

  return total;
};

const prices = [7, 1, 5, 3, 6, 4];
console.log(maxProfit(prices)) 
// Output: 7

Ending Note

This is a classic array problem and is often asked during interviews.

122. Best Time to Buy and Sell Stock II