InterviewBit Problems   Single Number II : Unsolved

About the Single Number II : Unsolved category (1)
TC : O(N) & SC : O(1) with easy & understandable code! (1)
Extra space allocation (5)
Sort(A.begin(),A.end()) gives error why? (3)
Explanation for the hint (3)
Why Bit? Sorting will also do it in O(32N) (2)
Expected Output and WA Explaination (2)
Partiial solution (1)
Question does not work on negative integers (1)
Shows time limit exceeds (2)
Can the number appear more than thrice? (3)
Find that single one = find that one element or find that element that appears o (2)