Easy_BestTimeToSellStock_122.java

package Leetcode;
/*
    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 (i.e., buy one and sell one share of the stock multiple times).
    Note: You may not engage in multiple transactions at the same time (i.e., you must sell the stock before you buy again).

    Example 1:

    Input: [7,1,5,3,6,4]
    Output: 7
    Explanation: Buy on day 2 (price = 1) and sell on day 3 (price = 5), profit = 5-1 = 4.
                 Then buy on day 4 (price = 3) and sell on day 5 (price = 6), profit = 6-3 = 3.
    Example 2:

    Input: [1,2,3,4,5]
    Output: 4
    Explanation: Buy on day 1 (price = 1) and sell on day 5 (price = 5), profit = 5-1 = 4.
                 Note that you cannot buy on day 1, buy on day 2 and sell them later, as you are
                 engaging multiple transactions at the same time. You must sell before buying again.
    Example 3:

    Input: [7,6,4,3,1]
    Output: 0
    Explanation: In this case, no transaction is done, i.e. max profit = 0.
 */
public class Easy_BestTimeToSellStock_122 {
    // 思路：双指针判断当前元素和其前一个元素的大小，如果大于就把差值加到profit上
    public int maxProfit(int[] prices) {
        if(prices.length == 0 || prices.length == 1)
            return 0;
        int profit = 0;
        for(int i = 1; i < prices.length; i++){
            if(prices[i] > prices[i-1])
                profit += prices[i] - prices[i-1];
        }
        return profit;
    }
}