BestTimeToBuyAndSellStock.js

// Source : https://leetcode.com/problems/best-time-to-buy-and-sell-stock
// Author : Dean Shi
// Date   : 2017-07-12

/***************************************************************************************
 *
 * Say you have an array for which the ith element is the price of a given stock on day
 * i.
 *
 * If you were only permitted to complete at most one transaction (ie, buy one and sell
 * one share of the stock), design an algorithm to find the maximum profit.
 *
 * Example 1:
 *
 * Input: [7, 1, 5, 3, 6, 4]
 * Output: 5
 *
 * max. difference = 6-1 = 5 (not 7-1 = 6, as selling price needs to be larger than
 * buying price)
 *
 * Example 2:
 *
 * Input: [7, 6, 4, 3, 1]
 * Output: 0
 *
 * In this case, no transaction is done, i.e. max profit = 0.
 *
 *
 ***************************************************************************************/

/**
 * @param {number[]} prices
 * @return {number}
 */
var maxProfit = function(prices) {
    let max = 0, min = prices[0]

    for (let p of prices) {
        min = Math.min(min, p)
        max = Math.max(max, p - min)
    }

    return max
};