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📚 Best Time to Buy and Sell Stock – Java Cheat Sheet

📌 What Is It?

The Best Time to Buy and Sell Stock problem involves finding the maximum profit you can achieve by buying and selling a stock. You are given an array where each element represents the stock price on a given day. You can only complete one transaction (buy one and sell one share).

🧱 Pattern Template

Greedy Algorithm

class Solution {
    public int maxProfit(int[] prices) {
        int minPrice = Integer.MAX_VALUE;
        int maxProfit = 0;

        for (int price : prices) {
            if (price < minPrice) {
                minPrice = price; // Update the minimum price
            } else if (price - minPrice > maxProfit) {
                maxProfit = price - minPrice; // Update the maximum profit
            }
        }

        return maxProfit;
    }
}

▶️ View Animation

📊 Time Complexity

• Time Complexity: O(N), where N is the number of days (length of the prices array).
• Space Complexity: O(1), as no additional space is used.

✅ Use Cases

• Optimizing profit in stock trading scenarios.
• Finding maximum differences in arrays with constraints.

📘 Common LeetCode Problems

• 121. Best Time to Buy and Sell Stock [Easy] Greedy

🧪 Example

Input: prices = [7, 1, 5, 3, 6, 4]
Output: 5

Explanation:
- Buy on day 2 (price = 1) and sell on day 5 (price = 6).
- Profit = 6 - 1 = 5.

💡 Pro Tips

• Track the minimum price encountered so far while iterating through the array.
• Calculate the profit for each day by subtracting the minimum price from the current price.
• Update the maximum profit whenever a higher profit is found.