Max Profit

Best Time to Buy and Sell Stock

LeetCode Problem 121

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) 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

Solution

const maxProfit = (prices: number[]): number => {
  let maxProfit = 0;
  let l = 0;
  let r = 1;
 
  while (r < prices.length) {
    const difference = prices[r] - prices[l];
    if (difference > 0) {
      maxProfit = Math.max(difference, maxProfit);
    } else {
      l = r;
    }
    r++;
  }
 
  return maxProfit;
};