Getting segmentation fault (core dump) for binary search(recursive) to find a number in an array

Question

This is a problem to find the target number in an array using the binary search recursive method. Getting segmentation fault. Have tried a lot but cannot find what is causing it. need some help to avoid such mistakes. which part is wrong in my code?? I have pasted the complete code.

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std ;


int recursivebinarysearch(vector <int>& arr ,int target , int ans ){
    int high = arr.size() - 1 ;
    int low = 0 ;
    int mid = (high + low) / 2 ;
    for(int i = 0 ; i < arr.size() ; i++){
        
        mid = (low+high)/2 ;
        if(low > high){
            mid = -1;
            return mid;
        }
        if(target > arr[mid]){
            low = mid +1 ;
            recursivebinarysearch(arr ,  target , ans );
        }
        else if(target < arr[mid]){
            high = mid -1;
            recursivebinarysearch(arr , target , ans );
        }
        else{
            mid = ans ;
            return ans ;
        }
    }
}
int main(){
    int n,   target , ans = 0;
    
    cin >> n  ;
    
    vector<int> arr ;
    int j = 0;
    for(int j = 0 ; j < n ; j++){
        cin >> arr[j];
    }
    cin >> target ;
    sort(arr.begin() , arr.end());
    ans = recursivebinarysearch(arr,  target , ans);

    cout<<ans<<endl;

    return 0;
}

Answer 1

high, low, mid are local to your function. So, each time you call recursivebinarysearch with the same vector arr, you get the same values. So, you infinitely recurse. The segmentation fault happens when the stack overflows.

If you want to keep this approach, you need to pass high and mid to the function and have it search this range only.

Alternatively, you can have a single while and adjust local values high, low as you go. This would be better, but some professors out there want to see explicit recursion.

Also, thanks to the comments, cin >> arr[j]; doesn't work. Either:

int value;
cin >> value;
arr.push_back(value);

or

arr.resize(j+1);
cin >> arr[j];