Compile time error in Binary Search Recursive implementation

Question

I am getting one compilation error in binary search recursive implementation

Here is my method:

public static int binarySearch(int[] a, int start, int end, int x) {
    if (start > end) {
      return -1;
    }
    int mid = (start + end) / 2;
    if (a[mid] == x) {
        return mid;
    } else if (a[mid] > x) {
        binarySearch(a, start, mid - 1, x);
    } else {
        binarySearch(a, mid + 1, end, x);
    }
}

I am giving two base case for this and returning two int values, but still i am getting error why this is happening . Any related thoughts'd be apprecited.

Thanks

What is the error exactly and where does it occur?

Sentry
– Sentry

2016-09-28 06:18:58 +00:00
Commented Sep 28, 2016 at 6:18 — Sentry
– Sentry, Commented Sep 28, 2016 at 6:18

nem035 · Accepted Answer · 2016-09-28 06:10:04Z

2

What do you think gets returned on the first call if both start > end and a[mid] == x are false?

You need to return your recursive calls as well so that the found value (or -1) will propagate back through the recursion stack frames:

public static int binarySearch(int[] a, int start, int end, int x) {
    if (start > end) {
        return -1;
    }
    int mid = (start + end) / 2;
    if (a[mid] == x) {
        return mid;
    } else if (a[mid] > x) {
        return binarySearch(a, start, mid - 1, x); // return here
    } else {
        return binarySearch(a, mid + 1, end, x);   // return here
    }

}

edited Sep 28, 2016 at 6:10

answered Sep 28, 2016 at 5:59

nem035

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Ketan G Over a year ago

literally stack overflow is a better place bcoz of u guys

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