Update 0518.零钱兑换2，添加C#

problems/0518.零钱兑换II.md

@@ -347,6 +347,26 @@ object Solution {
   }
 }
 ```
+### C#
+```csharp
+public class Solution
+{
+    public int Change(int amount, int[] coins)
+    {
+        int[] dp = new int[amount + 1];
+        dp[0] = 1;
+        for (int i = 0; i < coins.Length; i++)
+        {
+            for (int j = coins[i]; j <= amount; j++)
+            {
+                if (j >= coins[i])
+                    dp[j] += dp[j - coins[i]];
+            }
+        }
+        return dp[amount];
+    }
+}
+```
 
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