easyDSA

How do you find the best time to buy and sell a stock?

Q: How do you find the best time to buy and sell a stock?

**Intuition.** You want the biggest "sell minus buy" where the sell day comes *after* the buy day. Sweep once, tracking the **lowest price seen so far** — at each day the best profit if you sold today is price − minSoFar . Keep the maximum of those. prices [7,1,5,3,6,4] → buy at 1, sell at 6, profit 5 7 <text x="1

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Understand the problem

Maximize profit from a single buy/sell.

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Track the running minimum

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def max_profit(prices):
    min_price = float('inf')
    best = 0
    for price in prices:
        min_price = min(min_price, price)
        best = max(best, price - min_price)
    return best


# --- demo ---
print(max_profit([7, 1, 5, 3, 6, 4]))   # 5  (buy 1, sell 6)

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