Question

a. You need write a sequential search algorithm that is recursive format. b. Write a binary search algorithm that is recursive, then write the program to implement it.

C++

Answer 1

#include<iostream>
using namespace std;
int binarySearch(int arr[], int l, int r, int x)
{
if (r >= l) {
int mid = l + (r - l) / 2;
  
// If the element is present at the middle
// itself
if (arr[mid] == x)
return mid;
  
// If element is smaller than mid, than search left side else right side
if (arr[mid] > x)
return binarySearch(arr, l, mid - 1, x);
return binarySearch(arr, mid + 1, r, x);
}

//-1 if does not exist
return -1;
}
int binary_search_rec(int *p,int n,int x){
return binarySearch(p,0,n-1,x);
}

int linear_search_rec(int arr[], int n ,int key){
if(n<0) { // Base case - not found
return -1;
}
if(arr[n]==key) { // Base case - found
return n;
}
// Recursive case
return linear_search_rec(arr, n-1, key);
}
int main()
{
int arr[] = {10,20,30,55,67,88,98,110,150,170};
int size = 10;
int x=67;
int result = binary_search_rec(arr,size, x);
(result == -1) ? cout << "Element "
: cout << "Element is present at index " << result;

cout<<endl<<endl;
result = linear_search_rec(arr, size - 1, x);
(result == -1) ? cout << "Element is not present in array"
: cout << "Element is present at index " << result;
  
return 0;
}

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