L150 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).

Example

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

因为可以买卖多次，所以只要能赚钱就卖出。loop一边把所以差价加起来就是答案。

public int maxProfit(int[] prices) {
    if (prices == null || prices.length == 0) {
        return 0;
    }

    int res = 0;
    for (int i = 1; i < prices.length; i++) {
        int diff = prices[i] - prices[i - 1];
        if (diff > 0) {
            res += diff;
        }
    }

    return res;
}