121. Best Time to Buy and Sell Stock

📋 Đề Bài

You are given an array prices where prices[i] is the price of a given stock on the i^th day.

You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.

Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.

Example 1:

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.
Note that buying on day 2 and selling on day 1 is not allowed because you must buy before you sell.

Example 2:

Input: prices = [7,6,4,3,1]
Output: 0
Explanation: In this case, no transactions are done and the max profit = 0.

Constraints:

1 <= prices.length <= 10⁵
0 <= prices[i] <= 10⁴

💻 Lời Giải

C++ 0121-best-time-to-buy-and-sell-stock.cpp

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int profit = 0;
        int buy = INT_MAX;
        
        for (int price : prices) {
            profit = max(profit, price - buy);
            buy = min(buy, price);
        }
        
        return profit;
    }
};