121.Best_Time_to_Buy_and_Sell_Stock.java

class Solution {
    public int maxProfit(int[] prices) {
        int max = 0;
        int l=0;
        int r=1;
        while (r < prices.length) {
            if (prices[r] > prices[l]) {
                max = Math.max(max, prices[r]-prices[l]);
            } else {
                l = r;
            }
            r++;
        }

        return max;
    }
}