You are given an array prices where prices[i] is the price of a given stock on the ith day.
You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.
Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.
Example 1:
Input: prices = [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.
Note that buying on day 2 and selling on day 1 is not allowed because you must buy before you sell.
Solution
class Solution:
def maxProfit(self, prices: List[int]) -> int:
maxProfit = 0
lowest = prices[0]
for price in prices:
if price < lowest:
lowest = price
profit = price - lowest
maxProfit = max(maxProfit, profit)
return maxProfit- Keep track of max profit
- Start by setting the lowest price as the first element of the array (price on day 1)
- Iterate through the daily prices
- For a given price, if it’s lower than the lowest price we’ve seen before, update the lowest price
- Calculate the profit of this day by calculating
price - lowest - Compare this to the maximum profit we’ve seen, if it is more then we can update
Some things to note:
- If the
if price < lowestis triggered, the profit is zero for that day - Since we are finding the lowest amount based on our traversal of the array, we don’t have to deal with issues with selling before buying (there’s probably a better way to explain this)