121. Best Time to Buy and Sell Stock

/*
 * @lc app=leetcode id=121 lang=cpp
 *
 * [121] Best Time to Buy and Sell Stock
 *
 * https://leetcode.com/problems/best-time-to-buy-and-sell-stock/description/
 *
 * algorithms
 * Easy (54.33%)
 * Likes:    32079
 * Dislikes: 1225
 * Total Accepted:    5.6M
 * Total Submissions: 10.4M
 * Testcase Example:  '[7,1,5,3,6,4]'
 *
 * 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 <= 10^5
 * 0 <= prices[i] <= 10^4
 *
 *
 */

// @lc code=start
class Solution {
public:
    int maxProfit(vector<int>& prices)
    {
        int minCost = INT_MAX, maxProfit = 0;
        for (int price : prices)
        {
            minCost = min(price, minCost);
            maxProfit = max(maxProfit, price - minCost);
        }
        return maxProfit;
    }
};
// @lc code=end

• T: $O(N)$
• S: $O(1)$