[LeetCode 121] Best Time to Buy and Sell Stock

Problem

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 <= 105
- 0 <= prices[i] <= 104

TypeScript

function maxProfit(prices: number[]): number {
    if(prices.length === 0 || prices.length === 1) {
        return 0;
    }
    let res: number = 0;
    let left: number = 0, right: number = 1;
    
    while(right < prices.length) {
        if(prices[left] < prices[right]){
            let profit: number = prices[right] - prices[left];
            if(profit > res) {
                res = profit;
            }
        } else {
            left = right;
        }
        right++;
    }
    
    return res;
};

Reference

https://leetcode.com/problems/best-time-to-buy-and-sell-stock/