[LeetCode] Best Time to Buy and Sell Stock II

题目:

Say you have an array for which the i^th 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).

跟1版本类似，不同的地方在于1版本只允许买卖操作一次，而2版本允许多次买卖， 并且求得max profix

也是可以dp搞定

public class Solution {
    public int maxProfit(int[] prices) {
         if(prices.length<2) return 0;
        int n = prices.length;
        int[] ret = new int[n];
        ret[0] = 0;
        int buy = prices[0];
        int max = 0;
        for(int i=1;i<n;i++){
          if(prices[i]<=buy){
              buy = prices[i];
              ret[i] = ret[i-1];
          }
          else {
              ret[i] = prices[i] - buy + ret[i-1];
              buy = prices[i];
          }
        } 
        return ret[n-1];
    }
}