122. Best Time to Buy and Sell Stock II

Say you have an array for which the ith element is the price of a given stock on day i.

Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy one and sell one share of the stock multiple times). However, you may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).

Solution:

Whenever we find the stock price is higher than last day, we buy at last day and sell at current day.

For example, if the input prices are [1, 2, 3, 4, 5]

We do max = (2 - 1) + (3 - 2) + (4 - 3) + (5 - 4)

It is equivalent to max = 5 - 1.



Code:

public class Solution {
    public int maxProfit(int[] prices) {
        if (prices == null || prices.length == 0) {
            return 0;
        }
        int max = 0;
        for (int i = 1; i < prices.length; i++) {
            if (prices[i] > prices[i - 1]) {
                max += prices[i] - prices[i - 1];
            }
        }
        return max;
    }
}