0122买卖股票最佳时机2添加Java动态规划实现

problems/0122.买卖股票的最佳时机II（动态规划）.md

@@ -133,7 +133,34 @@ public:
 
 
 Java：
+```java
+// 动态规划
+class Solution 
+    public int maxProfit(int[] prices) {
+        int n = prices.length;
+        int[][] dp = new int[n][2];
+        dp[0][0] = 0;
+        dp[0][1] = -prices[0];
+        for (int i = 1; i < n; ++i) {
+            dp[i][0] = Math.max(dp[i - 1][0], dp[i - 1][1] + prices[i]);
+            dp[i][1] = Math.max(dp[i - 1][1], dp[i - 1][0] - prices[i]);
+        }
+        return dp[n - 1][0];
+    }
 
+    public int maxProfit(int[] prices) {
+        int n = prices.length;
+        int dp0 = 0, dp1 = -prices[0];
+        for (int i = 1; i < n; ++i) {
+            int newDp0 = Math.max(dp0, dp1 + prices[i]);
+            int newDp1 = Math.max(dp1, dp0 - prices[i]);
+            dp0 = newDp0;
+            dp1 = newDp1;
+        }
+        return dp0;
+    }
+}
+```
 
 Python：