121_ Best Time to Buy and Sell Stock

Problem

You are given an array prices where prices[i] is the price of a given stock on the ith 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

Solution

• maximum difference를 찾기

Code

C++

#include <vector>
#include <algorithm>

using namespace std;

class Solution
{
public:
    int maxProfit(vector<int> &prices)
    {
        int max_profit = 0;
        int min_price = INT_MAX;
        for (int i = 0; i < prices.size(); i++)
        {
            min_price = min(min_price, prices[i]);
            max_profit = max(max_profit, prices[i] - min_price);
        }
        return max_profit;
    }
};