121 best time to buy and sell stock

121. 买卖股票的最佳时机

go：

func maxProfit(prices []int) int {
    if len(prices) == 0 {
        return 0
    }
    minPrice, profit := prices[0], 0

    for i := 1; i < len(prices); i++ {
        if profit < prices[i] - minPrice {
            profit = prices[i] - minPrice
        }

        if prices[i] < minPrice {
            minPrice = prices[i]
        }
    }

    return profit
}