# 63.股票的最大利润

### 一、 题目

假设把某股票的价格按照时间先后顺序存储在数组中，请问买卖该股票一次可能获得的最大利润是多少？

示例 1:

输入: \[7,1,5,3,6,4]

输出: 5

解释: 在第 2 天（股票价格 = 1）的时候买入，在第 5 天（股票价格 = 6）的时候卖出，最大利润 = 6-1 = 5 。 注意利润不能是 7-1 = 6, 因为卖出价格需要大于买入价格。

示例 2:

输入: \[7,6,4,3,1]

输出: 0

解释: 在这种情况下, 没有交易完成, 所以最大利润为 0。

限制：

0 <= 数组长度 <= 10^5

来源：力扣（LeetCode）

链接：<https://leetcode-cn.com/problems/gu-piao-de-zui-da-li-run-lcof>

著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

### 二、 解法

```
func maxProfit(_ prices: [Int]) -> Int {
    guard prices.isEmpty == false else {
        return 0
    }
    var p = 0, res = 0, bottom = prices[0]
    
    while p < prices.count {
        let item = prices[p]
        if item <= bottom {
            bottom = item
        }
        else if item - bottom > res {
            res = item - bottom
        }
        p += 1
    }
    
    return res
}
```


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