Question

C++

Debug nextVowel.cpp

#include <iostream>

using namespace std;

// Recursion on a single value
// return next character (in ASCII order)
// which is a vowel, starting with parameter
// If there are no more vowels, return null character ('\0')
char nextVowel(char start) {
    // recursive call
    return nextVowel(start + 1);
    // base case
    if (start > 'z') return '\0';
    // incorrect base case
    if ('a' == start || 'i' == start
        || 'o' == start || 'u' == start)
            return start;
}

// Recursion on a group of values -- a vector

int main()
{
    char next;

    cout << "Simple recursion example with char's" << endl;
    cout << "Enter a starting char: ";
    cin >> next;
    next = nextVowel(next);
    if ('\0' == next)
        cout << "There was no next vowel" << endl;
    else cout << "The next vowel = " << next << endl;
    return 0;
}

Answer 1

Thanks for the question,

every time, we get a char, we must increment the char variable which is started by 1 and then check if its a vowel (in the if clause the start=='e' was missing) and if its a vowel we return the vowel else we must recursively call with the present value of start which was earlier incremented by 1

Also, the base case should be the first condition to be checked in a recursive call.

Below is the corrected code.

===========================================================================

#include <iostream>

using namespace std;

// Recursion on a single value
// return next character (in ASCII order)
// which is a vowel, starting with parameter
// If there are no more vowels, return null character ('\0')
char nextVowel(char start) {
  
// base case should be the first condition to be checked
if (start > 'z') return '\0';
// incorrect base case

start+=1; // increment by 1 to get the next character
if ('a' == start || 'i' == start || 'e'==start // e was missing added
|| 'o' == start || 'u' == start)
return start;
else{
   return nextVowel(start); // recursive call
   }
}

// Recursion on a group of values -- a vector

int main()
{
char next;

cout << "Simple recursion example with char's" << endl;
cout << "Enter a starting char: ";
cin >> next;
next = nextVowel(next);
if ('\0' == next)
cout << "There was no next vowel" << endl;
else cout << "The next vowel = " << next << endl;
return 0;
}

==============================================================================