Merge pull request #733 from ironartisan/master

添加121.买卖股票的最佳时机.mdJava解法

problems/0121.买卖股票的最佳时机.md

@@ -214,6 +214,26 @@ class Solution {
     }
 }
 ```
+```java
+// 解法1
+class Solution {
+    public int maxProfit(int[] prices) {
+        if (prices == null || prices.length == 0) return 0;
+        int length = prices.length;
+        // dp[i][0]代表第i天持有股票的最大收益
+        // dp[i][1]代表第i天不持有股票的最大收益
+        int[][] dp = new int[length][2];
+        int result = 0;
+        dp[0][0] = -prices[0];
+        dp[0][1] = 0;
+        for (int i = 1; i < length; i++) {
+            dp[i][0] = Math.max(dp[i - 1][0], -prices[i]);
+            dp[i][1] = Math.max(dp[i - 1][0] + prices[i], dp[i - 1][1]);
+        }
+        return dp[length - 1][1];
+    }
+}
+```
 
 ``` java
 class Solution { // 动态规划解法