Best Time to Buy and Sell Stock III

Tags : array, dynamic-programming, leetcode, cpp, hard

You are given an array prices where prices[i] is the price of a given stock on the ith day.

Find the maximum profit you can achieve. You may complete at most two transactions.

Note: You may not engage in multiple transactions simultaneously (i.e., you must sell the stock before you buy again).

Examples #

Example 1:

Input: prices = [3,3,5,0,0,3,1,4]
Output: 6
Explanation: Buy on day 4 (price = 0) and sell on day 6 (price = 3), profit = 3-0 = 3.
Then buy on day 7 (price = 1) and sell on day 8 (price = 4), profit = 4-1 = 3.

Example 2:

Input: prices = [1,2,3,4,5]
Output: 4
Explanation: Buy on day 1 (price = 1) and sell on day 5 (price = 5), profit = 5-1 = 4.
Note that you cannot buy on day 1, buy on day 2 and sell them later, as you are engaging multiple transactions at the same time. You must sell before buying again.

Example 3:

Input: prices = [7,6,4,3,1]
Output: 0
Explanation: In this case, no transaction is done, i.e. max profit = 0.

Example 4:

Input: prices = [1]
Output: 0

Constraints #

Solutions #


class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int b1=INT_MAX, b2=INT_MAX, s1=0, s2=0;
        for(int price: prices){
          b1 = min(b1,price);
          s1 = max(s1,price-b1);
          b2 = min(b2,price-s1);
          s2 = max(s2,price-b2);
        }
      return s2;
    }
};