Best Time to Buy/Sell Stock

👶 The 5-Year-Old Summary

Buy low, sell high! One buy, one sell. [7,1,5,3,6,4] → buy at 1, sell at 6 = profit 5!

🎮 Interactive Visualizer

prices = [7, 1, 5, 3, 6, 4]

🧠 The Brain Hack

Track minimum price so far! At each day, profit = current price - min price so far. Keep the max profit. This is like a sliding window of time!

💻 The Clean Solution

def max_profit(prices):
    min_price = float('inf')
    max_profit = 0
    
    for price in prices:
        # Update minimum price
        if price < min_price:
            min_price = price
        # Calculate profit if sold today
        else:
            profit = price - min_price
            max_profit = max(max_profit, profit)
    
    return max_profit

# [7,1,5,3,6,4] → 5 (buy at 1, sell at 6)

Time: O(n)

Space: O(1)