Question

C++ Recursive Functions:

Please call functions in a main function as well.

1. A recursive function that print the reverse of a string. (e.g., void

printReverse(string exp)). For example, if exp =”coding”, then the function

should print out “gnidoc”.

2. Implement a non-recursion-based binary search function. Convert this function

into a recursion-based function.

3. Implement a recursive and non-recursive Fibonacci function.

Answer 1

First of all we have to know about Recusrsive Funciton.

A recursive function is a function that calls itself during its execution. The process may repeat several times, outputting the result and the end of each iteration. The function Count() below uses recursion to count from any number between 1 and 9, to the number 10.

Answer for No.2

#include <stdio.h>

int binarySearch(int arr[], int l, int r, int x)

{

  while (l <= r)

  {

    int m = l + (r-l)/2;

    // Check if x is present at mid

    if (arr[m] == x)

        return m;  

    // If x greater, ignore left half  

    if (arr[m] < x)

        l = m + 1;

    // If x is smaller, ignore right half

    else

         r = m - 1;

  }

  // if we reach here, then element was not present

  return -1;

}

int main(void)

{

   int arr[] = {2, 3, 4, 10, 40};

   int n = sizeof(arr)/ sizeof(arr[0]);

   int x = 10;

   int result = binarySearch(arr, 0, n-1, x);

   (result == -1)? printf("Element is not present in array")

                 : printf("Element is present at index %d", result);

   return 0;

}

Answer for No.3

//Fibonacci Series using Recursion

#include<bits/stdc++.h>

using namespace std;

int fib(int n)

{

    if (n <= 1)

        return n;

    return fib(n-1) + fib(n-2);

}

int main ()

{

    int n = 9;

    cout << fib(n);

    getchar();

    return 0;

}