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买卖股票的最佳时机

Best Time to Buy and Sell Stock

专题
Algorithmic Programming / 算法编程
难度
L2
来源
Citadel

题目详情

问题：买卖股票的最佳时机

考察：数组、贪心

来源：Citadel

链接：https://www.jointaro.com/interviews/questions/best-time-to-buy-and-sell-stock/

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
解析

思路：从左到右维护到当前为止的最低买入价，用当前价格减最低价更新最大利润。卖出必须发生在买入之后，因此只需要一个历史最小值。

复杂度：时间 O(n)，空间 O(1)。