Count the number of vowels in C

Understanding Vowel Counting

Vowel counting involves determining the number of vowels (a, e, i, o, u) in a given string.

We will explore three different methods to count the vowels in a string using C.

Method 1: Using a Loop

This method iterates through the string and counts each vowel.

#include <stdio.h>
#include <ctype.h>

int countVowels(char *str) {
    int count = 0;
    for (int i = 0; str[i] != '\0'; i++) {
        char ch = tolower(str[i]);
        if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
            count++;
        }
    }
    return count;
}

int main() {
    char str[100];
    printf("Enter a string: ");
    gets(str);
    printf("Number of vowels: %d\n", countVowels(str));
    return 0;
}
            

Method 2: Using Recursion

This method counts vowels recursively.

#include <stdio.h>
#include <ctype.h>

int countVowelsRecursive(char *str, int index) {
    if (str[index] == '\0') return 0;
    char ch = tolower(str[index]);
    int count = (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') ? 1 : 0;
    return count + countVowelsRecursive(str, index + 1);
}

int main() {
    char str[100];
    printf("Enter a string: ");
    gets(str);
    printf("Number of vowels: %d\n", countVowelsRecursive(str, 0));
    return 0;
}
            

Method 3: Using Pointer

This method uses pointers to traverse the string and count vowels.

#include <stdio.h>
#include <ctype.h>

int countVowelsPointer(char *str) {
    int count = 0;
    while (*str) {
        char ch = tolower(*str);
        if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
            count++;
        }
        str++;
    }
    return count;
}

int main() {
    char str[100];
    printf("Enter a string: ");
    gets(str);
    printf("Number of vowels: %d\n", countVowelsPointer(str));
    return 0;
}