首页 > 代码库 > Leetcode-Best Time to Buy and Sell Stock III

Leetcode-Best Time to Buy and Sell Stock III

Say you have an array for which the ith element is the price of a given stock on day i.

Design an algorithm to find the maximum profit. You may complete at most two transactions.

Note:
You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).

Analysis:

We calculate two things:1. from day 0 to day i, what the maximum profit we can get by performing only one transcation. 2. from any day i to the end, what the maximum profit we can get by performing one transcation. We then find out the maximum profit by adding them up for each day.

Solution:

 1 public class Solution { 2     public int maxProfit(int[] prices) { 3         int len = prices.length; 4         if (len==0 || len==1) return 0; 5  6         int[] posProfit = new int[len]; 7         int[] negProfit = new int[len]; 8  9         int maxProfit = 0;10         int curProfit = 0;11         int minPrice = prices[0];12         for (int i=0;i<len;i++){13             if (minPrice>prices[i]) minPrice = prices[i];14             curProfit = prices[i]-minPrice;15             if (curProfit>maxProfit) maxProfit = curProfit;16             posProfit[i] = maxProfit;17         }18 19         maxProfit = 0;20         curProfit = 0;21         int maxPrice = prices[len-1];22         for (int i=len-1;i>=0;i--){23             if (maxPrice<prices[i]) maxPrice = prices[i];24             curProfit = maxPrice-prices[i];25             if (curProfit>maxProfit) maxProfit = curProfit;26             negProfit[i]=maxProfit;27         }28 29         int res = 0;30         for (int i=0;i<len;i++)31             if (res<posProfit[i]+negProfit[i]) res = posProfit[i]+negProfit[i];32 33         return res;34     }35 }

 

Leetcode-Best Time to Buy and Sell Stock III