121. Best Time to Buy and Sell Stock

[Tcdian]

121. Best Time to Buy and Sell Stock

给定一个数组，它的第 i 个元素是一支给定股票第 i 天的价格。

如果你最多只允许完成一笔交易（即买入和卖出一支股票一次），设计一个算法来计算你所能获取的最大利润。

注意你不能在买入股票前卖出股票。

Example 1

Input: [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.
             Not 7-1 = 6, as selling price needs to be larger than buying price.

Example 2

Input: [7,6,4,3,1]
Output: 0
Explanation: In this case, no transaction is done, i.e. max profit = 0.

[Tcdian]

Solution

• JavaScript Solution

/**
 * @param {number[]} prices
 * @return {number}
 */
var maxProfit = function(prices) {
    let profit = 0;
    let current = 0;
    for (let i = 1; i < prices.length; i++) {
        current += prices[i] - prices[i - 1];
        current = Math.max(0 , current);
        profit = Math.max(current, profit);
    }
    return profit;
};

• TypeScript Solution

function maxProfit(prices: number[]): number {
    let profit = 0;
    let current = 0;
    for (let i = 1; i < prices.length; i++) {
        current += prices[i] - prices[i - 1];
        current = Math.max(0, current);
        profit = Math.max(current, profit);
    }
    return profit;
};