Update 0941.有效的山脉数组.md

Author: Cwlrin

problems/0941.有效的山脉数组.md

@@ -177,7 +177,24 @@ function validMountainArray(arr: number[]): boolean {
 };
 ```
 
+## C#
 
+```csharp
+public class Solution {
+    public bool ValidMountainArray(int[] arr) {
+        if (arr.Length < 3) return false;
+
+        int left = 0;
+        int right = arr.Length - 1;
+
+        while (left + 1< arr.Length && arr[left] < arr[left + 1]) left ++;
+        while (right > 0 && arr[right] < arr[right - 1]) right --;
+        if (left == right && left != 0 && right != arr.Length - 1) return true;
+	
+        return false;
+    }
+}
+```
 
 
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