int maxProfit(vector<int>& prices) {

    int maxProfit=0;

    int left=0;

    int right=left+1;

    while(right<prices.size()){

        if(prices[left]>prices[right]){

            left=right;

            right++;

        }

        else{

            maxProfit=max(maxProfit,prices[right]-prices[left]);

            right++;

        }

​

     }

     return maxProfit;

    }

let prices = [7, 4, 5, 6, 7, 1, 2, 4, 2, 3, 4, 5, 6, 7, 2, 3]

​

//  Two pointers and flexible-size sliding window technique

//  Memory: O(1), Time: O(n)

const maxProfit = function (prices) {

    let l = 0

    let r = 1

    let profit = 0

    let min = Number.POSITIVE_INFINITY

    let max = Number.NEGATIVE_INFINITY

​

    while (r < prices.length) {

        if (min > prices[l]) {

            min = prices[l]

            max = Number.NEGATIVE_INFINITY

        }

​

        if (max < prices[r]) {

            max = prices[r]

        }

​

        if (profit < max - min) {

            profit = max - min

        }

​

        console.log(prices[l], prices[r], 'profit: ', profit)

​

        if (prices[l] <= prices[r]) {

            r++

        }

​

        if (prices[r - 1] > prices[r]) {

            l = r

            r++

        }

    }

​

    return profit

}

​

console.log(maxProfit(prices))

​

//  [Log]:

4 5 profit:  1

4 6 profit:  2

4 7 profit:  3

1 2 profit:  3

1 4 profit:  3

2 3 profit:  3

2 4 profit:  3

2 5 profit:  4

2 6 profit:  5

2 7 profit:  6

2 3 profit:  6

6

public class Buy_Sell_Stocks {

​

    public static int buy_sell_stocks(int[] prices) {

        int buying_price = Integer.MAX_VALUE;

        int Max_Profit = 0;

​

        for (int i = 0; i < prices.length; i++) {

            if (buying_price < prices[i]) {

                int profit = prices[i] - buying_price;

                Max_Profit = Math.max(Max_Profit, profit);

            } else {

                buying_price = prices[i];

            }

        }

        return Max_Profit;

    }

​

    public static void main(String[] args) {

        int[] arr = {7, 1, 5, 3, 6, 4};

​

        System.out.println(buy_sell_stocks(arr));

    }

}

​