[leetcode]121. Best Time to Buy and Sell Stock 最佳炒股时机

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 (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.

Note that you cannot sell a stock before you buy one.

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.

题目

给定一系列股价，允许买卖各一次。求最大收益。

思路

扫一遍input array，对于每个price： 更新当前minPrice， 更新当前maxProfit

代码

 class Solution {
     public int maxProfit(int[] prices) {
         if(prices.length < 2) return 0;
         int maxProfit = 0;
         int minPrice = prices[0];
         for(int price : prices){
             minPrice = Math.min(minPrice, price);
             maxProfit = Math.max(maxProfit, price - minPrice);
         }
         return maxProfit;
     }
 }