Count Vowels and Consonants in C

Summary: This C program counts the number of vowels and consonants in a given string. It processes the input character by character, checks if each character is a letter, and determines if it is a vowel or a consonant.

#include <stdio.h>
#include <string.h>

// Function to check if a character is a vowel
int isVowel(char ch) {
    // Convert to lowercase manually
    if (ch >= 'A' && ch <= 'Z') {
        ch = ch + 32;  // Convert uppercase to lowercase
    }

    // Check for vowels
    return (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u');
}

// Function to check if a character is an alphabet (manual check)
int isAlphabet(char ch) {
    return ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z'));
}

void countVowelsAndConsonants(char s[]) {
    int vowels = 0, consonants = 0;

    // Loop through each character of the string
    for (int i = 0; s[i] != '\0'; i++) {
        // Check if the character is an alphabet
        if (isAlphabet(s[i])) {
            // Check for vowels
            if (isVowel(s[i])) {
                vowels++;
            } 
            // Otherwise, it's a consonant
            else {
                consonants++;
            }
        }
    }

    // Print the results
    printf("Vowels: %d\n", vowels);
    printf("Consonants: %d\n", consonants);
}

int main() {
    char s[1001];  // String length limit 1000 + 1 for null terminator

    // Get the input string using scanf
    printf("Enter the string: ");
    scanf("%[^\n]%*c", s);  // Reads the entire line including spaces

    // Count vowels and consonants
    countVowelsAndConsonants(s);

    return 0;
}

Explanation:

Program Overview:

This program counts the number of vowels and consonants in a given string. It processes each character in the string to determine whether it is a vowel or a consonant.

Function - isVowel():

This function checks whether a character is a vowel.

• It converts uppercase characters to lowercase manually by adding 32 to their ASCII value.
• Checks if the character is any of 'a', 'e', 'i', 'o', or 'u'.

Function - isAlphabet():

This function checks whether a character is an alphabet.

• Checks if the character lies within the ranges 'A' to 'Z' or 'a' to 'z'.

Function - countVowelsAndConsonants():

This function counts the number of vowels and consonants.

• Loops through each character in the string.
• Checks if the character is an alphabet using isAlphabet().
• Uses isVowel() to determine if the character is a vowel.
• Increments the vowel or consonant counter accordingly.

Main Function Workflow:

1. Input the String:
   • The user enters a string, including spaces.
   • scanf("%[^\n]%*c", s) reads the entire line until a newline character.
2. Count Vowels and Consonants:
   • The function countVowelsAndConsonants() is called to count and print the results.

Edge Cases and Error Handling:

• Empty String: If the string is empty, both vowel and consonant counts are zero.
• Special Characters: Special characters and digits are ignored.

Time Complexity:

• O(n) where n is the length of the string since each character is processed once.

Space Complexity:

• O(1) as the operations are performed in-place with minimal extra space.