feat: add csharp solution to lc problem: No.0349 (#1924)

Author: Jahir509

solution/0300-0399/0349.Intersection of Two Arrays/README.md

@@ -183,6 +183,24 @@ class Solution {
 }
 ```
 
+### **C#**
+
+```cs
+public class Solution {
+    public int[] Intersection(int[] nums1, int[] nums2) {
+        List<int> result = new List<int>();
+        HashSet<int> arr1 = new(nums1);
+        HashSet<int> arr2 = new(nums2);
+        foreach (int x in arr1) {
+            if (arr2.Contains(x)) {
+                result.Add(x);
+            }
+        }
+        return result.ToArray();
+    }
+}
+```
+
 ### **...**
 
 ```

solution/0300-0399/0349.Intersection of Two Arrays/README_EN.md

@@ -165,6 +165,24 @@ class Solution {
 }
 ```
 
+### **C#**
+
+```cs
+public class Solution {
+    public int[] Intersection(int[] nums1, int[] nums2) {
+        List<int> result = new List<int>();
+        HashSet<int> arr1 = new(nums1);
+        HashSet<int> arr2 = new(nums2);
+        foreach (int x in arr1) {
+            if (arr2.Contains(x)) {
+                result.Add(x);
+            }
+        }
+        return result.ToArray();
+    }
+}
+```
+
 ### **...**
 
 ```

solution/0300-0399/0349.Intersection of Two Arrays/solution.cs

@@ -0,0 +1,13 @@
+public class Solution {
+    public int[] Intersection(int[] nums1, int[] nums2) {
+        List<int> result = new List<int>();
+        HashSet<int> arr1 = new(nums1);
+        HashSet<int> arr2 = new(nums2);
+        foreach (int x in arr1) {
+            if (arr2.Contains(x)) {
+                result.Add(x);
+            }
+        }
+        return result.ToArray();
+    }
+}