Best Time to Buy and Sell Stock

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).
Given an example
[2,1,2,0,1], return 2

变形题，题目变成可以进行多次交易，那我们只需要从头到尾遍历一遍，只要当天减去前一天是正的，我们就可以把值加入sum中。

class Solution {
    /**
     * @param prices: Given an integer array
     * @return: Maximum profit
     */
    public int maxProfit(int[] prices) {
        // write your code here
        if (prices == null || prices.length == 0) {
            return 0;
        }
        
        int sumProfit = 0;
        
        for (int i = 1; i < prices.length; i++) {
            int profit = prices[i] - prices[i-1];
            if(profit > 0){
                sumProfit += profit;
            }
        }
        return sumProfit;
    }
};