Checking if array is symmetric

Question

public class symm
{


/* 
 * Returns true if array A is symmetric.
 * Returns false otherwise.
 * n is the number of elements A contains.
 *
 * The running time of your algorithm is O(  ).
 * You may add a brief explanation here if you wish.
 */

 public static boolean symmetric( int[] A, int n )
 {
 return symmHelper(A, n, 0);

 }

private static boolean symmHelper(int[] A, int n, int i) {
if(n==1)
    return true;
if((n==2) && (A[i] == A[n-1-i]))
    return true;
if((i == n-1-i) && (A[i] == A[n-1-i] ))
    return true;    

if(A[i] == A[n-1-i] && i < n/2 )
    return symmHelper(A, n, i+1);

return false;
}  


}  

Test cases: I passed all the tests ecxept the fitst on I get no whenever I run it, I think the problem is that there are two 2s in the middle. And I'm not really sure about the code, I think it can be simplified. Is the running time o(log n)?

5 8 2 2 8 5 YES

10 7 50 16 20 16 50 7 10 YES

5 8 5 YES

1000 1000 YES

6000 YES

10 7 50 16 20 16 50 7 1000 NO

10 7 50 16 20 16 50 700 10 NO

10 7 50 16 20 16 5000 7 10 NO

10 7 50 16 20 1600 50 7 10 NO

10 7 50 16 1600 50 7 10 NO

Answer 1

if(A[i] == A[n-1-i] && i < n/2 )

That line right there is the problem. Because you're using an even number > 2 of values, when it gets to this line it skips over it because at that point i = n/2, rather than being less than it. So the function skips that and continues on to return false. Change it to this and you should be fine:

if(A[i] == A[n-1-i] && i <= n/2 )