<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):
        if len(prices) == 1:
            return 0
        elif len(prices) == 2:
            if prices[0] < prices[1]:
                return prices[1] - prices[0]
            else:
                return 0
        i = 1
        while len(prices) > 2 and i < len(prices) - 1:
            if prices[i - 1] <= prices[i] and prices[i] <= prices[i + 1] or prices[i - 1] >= prices[i] and prices[i] >= prices[i + 1]:
                del(prices[i])
                i -= 1
            i += 1
        if prices[0] > prices[1]:
           del(prices[0])
        if len(prices) % 2 == 1:
            del(prices[-1])
        if len(prices) <= 1:
            return 0
        elif len(prices) == 2:
            if prices[0] < prices[1]:
                return prices[1] - prices[0]
            else:
                return 0
        elif len(prices) == 3:
            return prices[1] - prices[0]
        else:
            i = 0
            while len(prices) > 3 and i < len(prices) - 3:
                if prices[i] <= prices[i + 2] and prices[i + 1] <= prices[i + 3]:
                    del(prices[i + 1])
                    del(prices[i + 1])
                    i -= 2
                elif prices[i] <= prices[i + 2] and prices[i + 1] >= prices[i + 3]:
                    del(prices[i + 2])
                    del(prices[i + 2])
                    i -= 2
                i += 2
            buy = prices[0]
            profit = 0
            for j in range(1, len(prices)):
                if prices[j] < buy:
                    buy = prices[j]
                elif prices[j] - buy > profit:
                    profit = prices[j] - buy
            return profit

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