<p>You are given an array <code>prices</code> where <code>prices[i]</code> is the price of a given stock on the <code>i<sup>th</sup></code> day.</p>

<p>You want to maximize your profit by choosing a <strong>single day</strong> to buy one stock and choosing a <strong>different day in the future</strong> to sell that stock.</p>

<p>Return <em>the maximum profit you can achieve from this transaction</em>. If you cannot achieve any profit, return <code>0</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> prices = [7,1,5,3,6,4]
<strong>Output:</strong> 5
<strong>Explanation:</strong> 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.
</pre>

<p><strong class="example">Example 2:</strong></p>

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

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= prices.length &lt;= 10<sup>5</sup></code></li>
	<li><code>0 &lt;= prices[i] &lt;= 10<sup>4</sup></code></li>
</ul>

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        left = 0
        right = 1
        max_diff = 0

        while right < len(prices):
            # print("Left: " + str(prices[left]) + "; Right: " + str(prices[right]))
            # if prices[right] - prices[left] > max_diff:
            #     max_diff = prices[right] - prices[left]
            if prices[left] < prices[right]: 
                profit = prices[right] - prices[left]
                max_diff = max(profit, max_diff) 
            else:
                left = right
            right += 1
            # print("Max: " + str(max_diff))

        return max_diff















        # l = 0
        # r = 1
        # maxprofit = 0

        # while r < len(prices): 
        #     if prices[l] >= prices[r]:
        #         l = r
        #     else: 
        #         profit = prices[r] - prices[l]
        #         maxprofit = max(maxprofit, profit)
        #     r += 1

        # return maxprofit



        
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