[leetcode]Best Time to Buy and Sell Stock II

 1 public class Solution {
 2     public int maxProfit(int[] prices) {
 3         if(prices == null || prices.length < 2) return 0;
 4         int pre = 0,  post = 1,length = prices.length;
 5         int buy = 0,profit = 0;
 6         for(int i = 0; i < prices.length; i++,pre = i - 1, post = i + 1){
 7             if(post < length && prices[pre] >= prices[i] && prices[post] > prices[i]){
 8                 buy = prices[i];
 9             }
10             if( prices[i] > prices[pre] && (post != length ? prices[i] >= prices[post] : true) ){
11                 profit += prices[i] - buy;
12             }
13         }
14         return profit;
15     }
16 }