How to correct my code of binary search in an array

Question

I was implementing a code for binary search in an array in java here is my code:

public class Exam {

    public static boolean find(int[]a, int k){

        int mid = a.length/2;
        if (a[mid]==k) {
            return true;
        }
        else if (a[mid] < k) {
            for (int i=0; i<a[mid]; i++) {
                if (a[i]==k) {
                    return true;
                } 
        }

        } else {
            for (int ii=mid; ii<a[a.length]; ii++) {
                if (a[ii]==k) {
                    return true;
                }
        }
    }
        return false;

    }

    public static void main(String[] args) {

        int[] a = { 2, 3, 4, 9, 11, 15 };

        System.out.println(find(a,3));

    }

}

When I run it I get error:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 6
    at shapes.Exam.find(Exam.java:20)
    at shapes.Exam.main(Exam.java:34)

But when I run this line instead:

System.out.println(find(a,15));

I get correct output as following:

true

What is the wrong with my code?

You're not doing binary search here; you're just searching half of the array. That's still has linear complexity. — Andy Turner, Nov 16 '16 at 23:03
Maybe we need some sort of codehomeworkhelp exchange. Would make these easier to deal with. — Jeutnarg, Nov 16 '16 at 23:04

score -1 · Answer 1 · answered Nov 16 '16 at 23:03

-1

Here:

 for (int ii=mid; ii<a[a.length]; ii++) {

for last element of an array it should be a[a.length-1]

answered Nov 16 '16 at 23:03

Antoniossss

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does not work. I get same error. thanks – Joe Nov 16 '16 at 23:04
`mid` is the index of the middle element of the array. What is `a[a.length]` or `a[a.length - 1]`? – Andy Turner Nov 16 '16 at 23:06
@AndyTurner logicly IDK, semanticly reason for given exception. – Antoniossss Nov 16 '16 at 23:08
You'd still get an `ArrayIndexOutOfBoundsException` with that change - for a different reason, but the same exception. – Andy Turner Nov 16 '16 at 23:09

How to correct my code of binary search in an array

1 Answers1