121 - Best Time To Buy And Sell Stock

#easy

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.

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int max_result = 0;
        int min_buy = INT_MAX;
        for ( int i = 0; i < prices.size(); i++ ) {
            if ( min_buy > prices[i] ) min_buy = prices[i];
            else if ( prices[i] - min_buy > max_result ) max_result = prices[i] - min_buy;
        }

        return max_result;
    }
};