How to delete the vowels from a given string using C language?

In C, removing vowels from a string involves iterating through each character and shifting non-vowel characters to form a new string without vowels. This can be accomplished by checking each character against the vowel set and either skipping or keeping it.

Syntax

for(i=0; i<length; i++) {
    if(character is not a vowel) {
        result[j++] = str[i];
    }
}

Method 1: Using Character Shifting

This approach removes vowels by shifting characters within the original string −

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

int main() {
    char str[] = "TutorialsPoint";
    int len = strlen(str);
    int i, j;
    
    printf("Original String: %s
", str);
    
    for(i = 0; i < len; i++) {
        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') {
            for(j = i; j < len; j++) {
                str[j] = str[j + 1];
            }
            len--;
            i--;  /* Check the same position again */
        }
    }
    
    printf("After removing vowels: %s
", str);
    return 0;
}

Original String: TutorialsPoint
After removing vowels: TtrlsPnt

Method 2: Using Two-Pointer Approach

This method uses two indices to build the result more efficiently −

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

int isVowel(char c) {
    return (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u' ||
            c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U');
}

int main() {
    char str[] = "Hello World Programming";
    int len = strlen(str);
    int i, j = 0;
    
    printf("Original String: %s
", str);
    
    for(i = 0; i < len; i++) {
        if(!isVowel(str[i])) {
            str[j] = str[i];
            j++;
        }
    }
    str[j] = '\0';  /* Null terminate the result */
    
    printf("After removing vowels: %s
", str);
    return 0;
}

Original String: Hello World Programming
After removing vowels: Hll Wrld Prgrmmng

Comparison

Key Points

• The two-pointer approach is more efficient with O(n) time complexity.
• Always null-terminate the result string using '\0'.
• Check both uppercase and lowercase vowels for complete removal.
• The character shifting method requires decrementing the index when a vowel is found.

Conclusion

Removing vowels from a string in C can be done efficiently using the two-pointer approach. This method preserves the original string structure while eliminating all vowel characters in a single pass.