Q12: Best Time to Buy and Sell Stock (I & II). - DSA Patterns (Multi-Lang)

In Simple Words:

Part I (One Transaction): Track minPrice seen so far and update maxProfit = max(maxProfit, price - minPrice).
Part II (Unlimited Transactions): Accumulate all positive price differences price[i] - price[i-1] greedily.
Time: $O(N)$ | Space: $O(1)$

Multi-Language SolutionsPython 3 • JavaScript • TypeScript • Java • C++

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def maxProfitPartI(prices: list[int]) -> int:
    min_price = float('inf')
    max_p = 0
    for p in prices:
        min_price = min(min_price, p)
        max_p = max(max_p, p - min_price)
    return max_p

def maxProfitPartII(prices: list[int]) -> int:
    profit = 0
    for i in range(1, len(prices)):
        if prices[i] > prices[i - 1]:
            profit += prices[i] - prices[i - 1]
    return profit