C++ Program to Check Vowel or Consonant

In C++, you can check if a character is a vowel or consonant by using if statements to compare the character against vowels like 'a', 'e', 'i', 'o', 'u' (both lowercase and uppercase), and print the result accordingly.

Examples

Inputa

Outputa is a vowel

InputB

OutputB is a consonant

Input1

Output1 is not an alphabet

How to Think About It

To decide if a character is a vowel or consonant, first check if it is a letter. If it is not a letter, say it is not an alphabet. If it is a letter, compare it to vowels (a, e, i, o, u) in both lowercase and uppercase. If it matches any vowel, it is a vowel; otherwise, it is a consonant.

Algorithm

1

Get a single character input from the user.

2

Check if the character is an alphabet letter.

3

If not an alphabet, print it is not an alphabet and stop.

4

If it is an alphabet, check if it matches any vowel (a, e, i, o, u) ignoring case.

5

If it matches a vowel, print it is a vowel.

6

Otherwise, print it is a consonant.

Code

cpp

#include <iostream>
using namespace std;

int main() {
    char ch;
    cout << "Enter a character: ";
    cin >> ch;

    if (!((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z'))) {
        cout << ch << " is not an alphabet" << endl;
    } else if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u' ||
               ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U') {
        cout << ch << " is a vowel" << endl;
    } else {
        cout << ch << " is a consonant" << endl;
    }
    return 0;
}

Output

Enter a character: a
a is a vowel

Dry Run

Let's trace the input 'a' through the code

1

Input character

User inputs 'a'

2

Check if alphabet

'a' is between 'a' and 'z', so it is an alphabet

3

Check if vowel

'a' matches vowel 'a'

4

Print result

Print 'a is a vowel'

Step	Condition Checked	Result
2	'a' is alphabet?	True
3	'a' is vowel?	True
4	Print output	'a is a vowel'

Why This Works

Step 1: Check if character is alphabet

We use if to see if the character is between 'A' and 'Z' or 'a' and 'z' to confirm it is a letter.

Step 2: Check vowels

We compare the character with vowels in both lowercase and uppercase using if and || operators.

Step 3: Print result

If it matches a vowel, print it is a vowel; otherwise, print it is a consonant.

Alternative Approaches

Using switch-case

cpp

#include <iostream>
#include <cctype>
using namespace std;

int main() {
    char ch;
    cout << "Enter a character: ";
    cin >> ch;

    if (!((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z'))) {
        cout << ch << " is not an alphabet" << endl;
    } else {
        switch(tolower(ch)) {
            case 'a': case 'e': case 'i': case 'o': case 'u':
                cout << ch << " is a vowel" << endl;
                break;
            default:
                cout << ch << " is a consonant" << endl;
        }
    }
    return 0;
}

This uses <code>switch</code> and <code>tolower</code> to simplify vowel checking and improve readability.

Using string find

cpp

#include <iostream>
#include <string>
#include <cctype>
using namespace std;

int main() {
    char ch;
    string vowels = "aeiouAEIOU";
    cout << "Enter a character: ";
    cin >> ch;

    if (!isalpha(ch)) {
        cout << ch << " is not an alphabet" << endl;
    } else if (vowels.find(ch) != string::npos) {
        cout << ch << " is a vowel" << endl;
    } else {
        cout << ch << " is a consonant" << endl;
    }
    return 0;
}

This uses a string of vowels and <code>find</code> method to check membership, making the code concise.

Complexity: O(1) time, O(1) space

Time Complexity

The program runs in constant time because it only checks a single character with fixed comparisons.

Space Complexity

The program uses constant space for variables and no extra data structures.

Which Approach is Fastest?

All approaches run in O(1) time; using switch or string find improves readability but does not affect speed significantly.

Approach	Time	Space	Best For
If-else comparisons	O(1)	O(1)	Simple and direct checks
Switch-case with tolower	O(1)	O(1)	Cleaner code with multiple cases
String find method	O(1)	O(1)	Concise code using standard library