[LeetCode] 122. Best Time to Buy and Sell Stock II

Best Time to Buy and Sell Stock II

Link to original Problem on LeetCode

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 as many transactions as you like (i.e., buy one and sell one share of the stock multiple times).

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

Example 1:

Input: [7,1,5,3,6,4]

Output: 7

Explanation: Buy on day 2 (price = 1) and sell on day 3 (price = 5), profit = 5-1 = 4. Then buy on day 4 (price = 3) and sell on day 5 (price = 6), profit = 6-3 = 3.

Example 2:

Input: [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: [7,6,4,3,1]

Output: 0

Explanation: In this case, no transaction is done, i.e. max profit = 0.

Company: Amazon

Solution

Time Complexity: O(n) Space Complexity: O(1)

class Solution(object):
    def maxProfit(self, prices):
        """
        :type prices: List[int]
        :rtype: int
        """
        # We solve this problem using greedy solution
        # Every time we see price of the stock which is less than the price of stock next day,
        # We buy and sell the stock and add it up to the profit

        profit = 0

        for i in range(len(prices) - 1):
            if prices[i] < prices[i + 1]:
                profit += prices[i + 1] - prices[i]
                
        return profit