Merge pull request #2129 from Lozakaka/patch-21

新增java 2*2 array solution

problems/0714.买卖股票的最佳时机含手续费（动态规划）.md

@@ -154,6 +154,25 @@ class Solution {
     return dp[1];
     }
 }
+```Java
+//使用 2*2 array
+class Solution {
+    public int maxProfit(int[] prices, int fee) {
+        int dp[][] = new int[2][2];
+        int len = prices.length;
+        //[i][0] = holding the stock
+        //[i][1] = not holding the stock
+        dp[0][0] = -prices[0];
+
+        for(int i = 1; i < len; i++){
+            dp[i % 2][0] = Math.max(dp[(i - 1) % 2][0], dp[(i - 1) % 2][1] - prices[i]);
+            dp[i % 2][1] = Math.max(dp[(i - 1) % 2][1], dp[(i - 1) % 2][0] + prices[i] - fee);
+        }
+
+        return dp[(len - 1) % 2][1];
+    }
+}
+```
 ```
 
 Python：