C Program to Count the Number of Vowels in a String
C program to count the number of vowels in a string.
In this article we will learn a simple C program to count the number of vowels in a string.
‘A’, ‘E’, ‘I’, ‘O’, ‘U’ are five vowels out of 26 characters in English alphabet letters.C programming is case sensitive, and hence lowercase and uppercase characters are considered differently, so we will have to check for both the cases.
Methods discussed
Problem Statement – Write a program to calculate total number of vowels in a sentence
We are going to discuss to methods in this post –
- Iterative Method
- Recursive Method
Algorithm
- Initialize the variable.
- Accept the input.
- Initialize for loop.
- Check and count the vowels.
- Terminate for loop.
- Print total count.
Method 1 (Iterative)
Run
#include <stdio.h>
#include <ctype.h>
int main()
{
// Initializing variable.
char str[100];
int i, vowels = 0;
// Accepting input.
printf("Enter the string: ");
// best way to read string rather than gets/fgets
scanf("%[^\n]s",&str);
//Initializing for loop.
for(i = 0; str[i]; i++)
{
//Counting the vowels.
if(str[i]=='a'|| str[i]=='e'||str[i]=='i'||
str[i]=='o'|| str[i]=='u'||str[i]=='A'||
str[i]=='E'||str[i]=='I'||str[i]=='O' ||str[i]=='U')
{
vowels++;
}
}
//Printing the count of vowels.
printf("Total number of vowels: = %d\n",vowels);
return 0;
}
Enter the string: I am human Total number of vowels: = 4
Note
The time complexity of above code in O(n) as in the code we are looping over the string once.
Method 2 (Recursive)
This method uses recursion in C
Additionally, we have used another function to convert the character into the upper case so we do not have to write separate ‘OR’ conditions of lowercase characters
Run
#include <stdio.h>
#include <ctype.h>
#include <string.h>
// toupper function is available in ctype.h header file
// Function to check the Vowel
int isVowel(char ch)
{
ch = toupper(ch);
return (ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U');
}
// to count total number of vowel from 0 to n
int countVowel(char str[], int n)
{
if (n == 1)
return isVowel(str[n - 1]);
return countVowel(str, n - 1) + isVowel(str[n - 1]);
}
int main() {
// string object
char str[10] = "Hey Dude";
int len = strlen(str);
// Total numbers of Vowel
printf("%d", countVowel(str, len));
return 0;
}
Output
3
Note
The time complexity of above code is also O(N) as total n recursive calls are made. Where N is length of string
Juggling algorithm for array rotation
Method 3 (Using a Function)
Below is another way of counting vowels in a string using a function –
Run
// Count Vowels using a function
#include <stdio.h>
#include <ctype.h>
// toupper/tolower function is available in ctype.h header file
int isVowel(char ch)
{
// reduce number of or cases of upper / lower cases
// by converting input char to lowercase or uppercase
ch = tolower(ch);
if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u')
return 1;
return 0;
}
int getVowelCount(char a[])
{
int count = 0, i = 0;
char ch;
while (a[i] != '\0'){
ch = a[i];
if (isVowel(ch))
count++;
i++;
}
return count;
}
int main()
{
char str[100];
printf("Enter a string\n");
// best way to read string rather than gets/fgets
scanf("%[^\n]s",&str);
// gets(str); do not use this
printf("Total Vowels: %d\n", getVowelCount(str));
return 0;
}
Output
Enter a string
i am human
Total Vowels: 4
Method 4 (Program to count vowels, consonants, whitespaces, digits)
Run
#include <stdio.h>
#include <ctype.h>
// toupper/tolower function is available in ctype.h header file
int main() {
char str[100];
int vowels = 0, consonants = 0, digits = 0, whitespaces = 0, special = 0;
// get full line of string input
printf("Enter string: \n");
fgets(str, sizeof(str), stdin);
// can also use this instead of fgets
// scanf("%[^\n]s",&str);
// loop through each character of the string
for (int i = 0; str[i] != '\0'; ++i) {
// convert to uppercase
str[i] = toupper(str[i]);
// checking for a vowel
if (str[i] == 'A' || str[i] == 'E' || str[i] == 'I' ||
str[i] == 'O' || str[i] == 'U') {
// increment value of vowels by 1
vowels++;
}
// if its b/w A-Z and wasn't vowel then its a consonant
else if ((str[i] >= 'A' && str[i] <= 'Z')) {
consonants++;
}
// checking for a digit
else if (str[i] >= '0' && str[i] <= '9') {
digits++;
}
// checking for a whitespace
else if (str[i] == ' ') {
whitespaces++;
}
}
printf("Total No. of Vowels: %d\n", vowels);
printf("Total No. of Consonants: %d\n", consonants);
printf("Total No. of Digits: %d\n", digits);
printf("Total No. of White spaces: %d\n", whitespaces);
return 0;
}
Output
Enter string:
I am a human 1001
Total No. of Vowels: 5
Total No. of Consonants: 4
Total No. of Digits: 4
Total No. of White spaces: 4
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