best-time-to-buy-and-sell-stock.py

# -*- coding:utf-8 -*-


# 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.
#
#
# Example 2:
#
#
# Input: [7,6,4,3,1]
# Output: 0
# Explanation: In this case, no transaction is done, i.e. max profit = 0.
#
#


class Solution(object):
    def maxProfit(self, prices):
        """
        :type prices: List[int]
        :rtype: int
        """
        if not prices:
            return 0
        
        profit = 0
        cur = prices[0]
        for item in prices[1:]:
            result = item - cur
            if result <= 0:
                cur = item
            else:
                if result > profit:
                    profit = result
        
        return profit