// 121. Best Time to Buy and Sell Stock

// 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

// Runtime: 1 ms, faster than 100.00% of Java online submissions for Best Time to Buy and Sell Stock.

// Memory Usage: 52.2 MB, less than 58.79% of Java online submissions for Best Time to Buy and Sell Stock.

class Solution {

public int maxProfit(int[] prices) {

if (prices.length < 2) return 0;

int max = 0;

int diff = 0;

int minBuy = prices[0];

int sell = prices[0];

for (int i = 1; i < prices.length; i++) {

if (prices[i] < minBuy) {

minBuy = prices[i];

} else if (prices[i] - minBuy > max) {

diff = prices[i] - minBuy;

if (diff > max) max = diff;

}

}

return max;

}

}