Day i do not know

136. Single Number/Solution.cs

@@ -0,0 +1,12 @@
+namespace _136._Single_Number;
+
+public class Solution
+{
+    public int SingleNumber(int[] nums)
+    {
+        int res = 0;
+        foreach (int num in nums)
+            res ^= num;
+        return res;
+    }
+}