Python Scenario-Based Interview Question: Find Maximum Profit from Stock Prices

Python programming interviews often include scenario-based coding problems that test logical thinking and optimization skills. One of the most popular problems is calculating the maximum profit from stock prices by buying at one time and selling later.

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 Problem Scenario

You are given stock prices with timestamps:

prices = [
    ("2026-03-29 09:30:00", 150.25),
    ("2026-03-29 09:31:00", 152.10),
    ("2026-03-29 09:32:00", 151.80),
    ("2026-03-29 09:33:00", 154.50)
]

Question: Find the maximum profit by buying at one price and selling at a later higher price.

Expected Output:

4.25  # Buy at 150.25 (09:30), Sell at 154.50 (09:33)

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🐍 Python Code Solution

max_profit = 0
min_price = prices[0][1]

for time, price in prices[1:]:
    profit = price - min_price
    max_profit = max(max_profit, profit)
    min_price = min(min_price, price)

print(f"{max_profit:.2f}")

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 Step-by-Step Explanation

1. Initialize Variables

• max_profit is set to 0
• min_price stores the lowest price seen so far

2. Loop Through Prices

We iterate through each price and calculate potential profit.

3. Calculate Profit

profit = price - min_price

4. Update Maximum Profit

max_profit = max(max_profit, profit)

5. Update Minimum Price

min_price = min(min_price, price)

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 Time and Space Complexity

Complexity	Value
Time Complexity	O(n)
Space Complexity	O(1)

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 Real-World Applications

• Stock market trading systems
• Financial analysis tools
• Cryptocurrency tracking
• Trading bots
• Investment software

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 Why Interviewers Ask This Question

• Tests problem-solving ability
• Checks algorithm optimization
• Evaluates logical thinking
• Measures coding efficiency

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 Example Walkthrough

Time	Price	Min Price	Profit	Max Profit
09:30	150.25	150.25	0	0
09:31	152.10	150.25	1.85	1.85
09:32	151.80	150.25	1.55	1.85
09:33	154.50	150.25	4.25	4.25

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 Alternative Python Function

def max_profit(prices):

    max_profit = 0
    min_price = prices[0][1]

    for time, price in prices:

        if price < min_price:
            min_price = price

        elif price - min_price > max_profit:
            max_profit = price - min_price

    return max_profit

print(max_profit(prices))

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 Edge Cases

• Prices always decreasing
• Only one price available
• Empty list
• Same price values

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📚 Related Python Interview Questions

• Python Password Generator Project
• Sales Data Analysis in Python
• Python Variables in Hindi

❓ Frequently Asked Questions (FAQ)

What is the time complexity of this algorithm?

The time complexity is O(n) because we iterate through the list once.

Can this problem be solved using Python?

Yes, Python provides simple loops and conditions to efficiently solve this problem.

Is this question asked in coding interviews?

Yes, it is a classic interview question known as "Best Time to Buy and Sell Stock".

 Practice this problem to improve Python interview skills!