Buy and Sell Stocks 1

Say you have an array for which the i-th element is the price of a given stock on day i.

If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.

Note that you cannot sell a stock before you buy one.

Example:

Input: [7,1,5,3,6,4]
Output: 5
Explanation: Buy on day 2 (price = 1) and sell on 5 (price = 6) with profit = 5

Write your solution:

function main (prices) {
    return;
}

function main (prices) { return; }

Test Case 1

Input: [7,1,5,3,6,4]
Output: 5

Test Case 2

Input: [7,6,4,3,1]
Output: 0

Solution

Complexity:

• Time complexity: O(n)
• Space complexity: O(1)

function maxProfit(prices) {
    let minPrice = Number.MAX_SAFE_INTEGER;
    let maxProfit = 0;

    prices.forEach((price) => {
        if (price < minPrice) {
            minPrice = price;
        } else if (price - minPrice > maxProfit) {
            maxProfit = price - minPrice;
        }
    });

    return maxProfit;
}