Update single_number.cpp

Author: avidLearnerInProgress

single_number.cpp

@@ -1,5 +1,7 @@
 class Solution:
-    int singleNumber(vector<int> &nums):
+    int singleNumber(vector<int> &nums){
         int x = 0;
         for(auto num : nums) x ^= num;
         return x;
+    }
+};