121. Best Time to Buy and Sell Stock

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

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.

Example 2:

• Input: prices = [7,6,4,3,1]
• Output: 0
• Explanation: In this case, no transactions are done and the max profit = 0.

Constraints:

• 1 <= prices.length <= 10^5
• 0 <= prices[i] <= 10^4

Approach

Solution

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        left = min(prices)
        for right in range(len(prices)):
            while curr > left:
                curr -= prices[left]
                left += 1
            ans = max(ans, curr)
        return ans

Explanation