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easyDSA

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

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01

Understand the problem

Maximize profit from a single buy/sell.

arraysgreedy
02

Attempt it yourself

Sketch your approach before reading the solution — that's what interviews test.

Nudge consolestandby

Stuck? Beam a request up — the console returns a conceptual nudge that guides your logic without spoiling the implementation.

03

Study the solution

Track the minimum price seen so far and, at each day, compute price - minSoFar to update the best profit. One pass updates both, giving O(n) time and O(1) space. The trick is realizing you only need the lowest price to the left of each selling day.

Solution ready — 2 min read

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04

Read the code

Track the running minimum
Run Playground
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)
05

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Transmission complete // awaiting log

KEEP THE
STREAK ALIVE.

Dossier 9 of 127 decoded in the Data Structures & Algorithms track. One more won't hurt.

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