update 0121 and 0122

problems/0121.买卖股票的最佳时机.md

@@ -464,6 +464,47 @@ function maxProfit(prices: number[]): number {
 };
 ```
 
+C#：
+
+> 贪心法
+
+```csharp
+public class Solution
+{
+    public int MaxProfit(int[] prices)
+    {
+        int min = Int32.MaxValue;
+        int res = 0;
+        for (int i = 0; i < prices.Length; i++)
+        {
+            min = Math.Min(prices[i], min);
+            res = Math.Max(prices[i] - min, res);
+        }
+        return res;
+    }
+}
+```
+
+> 动态规划
+
+```csharp
+public class Solution
+{
+	public int MaxProfit(int[] prices)
+    {
+        int[] dp = new int[2];
+        int size = prices.Length;
+        (dp[0], dp[1]) = (-prices[0], 0);
+        for (int i = 0; i < size; i++)
+        {
+            dp[0] = Math.Max(dp[0], -prices[i]);
+            dp[1] = Math.Max(dp[1], dp[0]+prices[i]);
+        }
+        return dp[1];
+    }
+}
+```
+
 
 
 
@@ -471,3 +512,4 @@ function maxProfit(prices: number[]): number {
 <a href="https://programmercarl.com/other/kstar.html" target="_blank">
   <img src="../pics/网站星球宣传海报.jpg" width="1000"/>
 </a>
+