69. Best Time to Buy and Sell Stock

Easy

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Companies

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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:

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Track the minimum price seen so far and the maximum profit. For each price, calculate the profit if we sell at that price (current price - minimum price). Update the maximum profit if this profit is greater.

Time Complexity

O(n)

Space Complexity

O(1)