1 class Solution {
 2 public:
 3     int singleNumber(int A[], int n) {
 4         int i,j;
 5         for(i=0; i<n; i++)
 6         {
 7             for(j=i+1; j<n; j++)
 8             {
 9                 if(A[j]==A[i])
10                 {
11                     int temp = A[i+1];
12                     A[i+1] = A[j];
13                     A[j] = temp;
14                     i++;
15                     break;
16                 }
17             }
18             if(j==n)
19                 return A[i];    
20         }
21     }
22 };

1 class Solution {
2 public:
3     int singleNumber(int A[], int n) {
4         int result=0;
5         for(int i=0; i<n; i++)
6             result = result ^ A[i];
7         return result;
8     }
9 };