Best Time to Buy and Sell Stock

Leetcode Problem 121: Best Time to Buy and Sell Stock

Problem Summary

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.

Techniques

• Single pass through the array
• Track the minimum price seen so far
• Calculate the maximum profit achievable

Solution

function maxProfit(prices: number[]): number {
    let minPrice = Infinity
    let maxProfit = 0

    for(let i = 0; i < prices.length; i++) {
        if (prices[i] < minPrice) {
            minPrice = prices[i]
        } else {
            maxProfit = Math.max(maxProfit, prices[i] - minPrice)
        }
    }

    return maxProfit
}

console.log(maxProfit([7,1,5,3,6,4]))