121. Best Time to Buy and Sell Stock

Question

LeetCode Problem

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

Solutions

int maxProfit(vector<int>& prices) {
	int maxProfit_ = INT32_MIN;
	int minPrice = INT32_MAX;
	for (auto& p : prices) {
		minPrice = min(minPrice, p);
		int profit = p - minPrice;
		if (profit > 0) {
			maxProfit_ = max(maxProfit_, profit);
		}
	}
	return maxProfit_;
}