CODEWITHSUNDEEP
javasearchbinary
user3862389
user3862389

Reputation:

Binary Search Using Recusion

I am trying to create a binary search algorithm using recursion in Java, when debugging everything seems to be okay up until it finds the value and should return the index of the key needed. However, for some reason it skips the return statement and goes to the bottom return statement.

public int binSearch(int key, int L, int R) {

    int mid =(R + L)/2;

    if (R < L) {
        return -1;
    }

    if (A[mid] == key) {
        return mid;
    }

    if (key > A[mid]) {
        binSearch(key, mid + 1, R);
    }

    if (key < A[mid]) {
        binSearch(key, L, mid - 1);
    }
   return -1;
}

Upvotes: 0

Views: 52

Answers (2)

B. Cratty
B. Cratty

Reputation: 1993

I was able to salvage this from an old post. I know it doesnt fix your problem, but it shows you another way to solving this problem.

public static int binarySearch(int[] a, int target) {
    return binarySearch(a, 0, a.length-1, target);
}

public static int binarySearch(int[] a, int start, int end, int target) {
    int middle = (start + end) / 2;
    if(end < start) {
        return -1;
    } 

    if(target==a[middle]) {
        return middle;
    } else if(target<a[middle]) {
        return binarySearch(a, start, middle - 1, target);
    } else {
        return binarySearch(a, middle + 1, end, target);
    }
}

Upvotes: 1

user10367961
user10367961

Reputation:

You are missing some return statements (when you are invoking binSearch recursively)

public int binSearch(int key, int L, int R) {
    int mid =(R + L)/2;
    if (R < L) {
        return -1;
    }
    if (A[mid] == key) {
        return mid;
    }
    if (key > A[mid]) {
        return binSearch(key, mid + 1, R);
    }
    if (key < A[mid]) {
        return binSearch(key, L, mid - 1);
    }
    return -1;
}

Upvotes: 0

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