Program to remove consonants from a String

Given a string , the task is to remove all the consonants from the string and then print the string.

Examples:

Input: str= “Welcome to geeksforgeeks” 
Output: eoe o eeoee

Input: str= “What is your name?” 
Output: a i ou ae? 

Approach: Traverse all the characters of the string, if the character is a consonant then remove it from the final answer.

Below is the implementation of the above approach:

C++

// C++ program to remove
// all the consonants
#include <bits/stdc++.h>
using namespace std;

// function that returns true
// if the character is an alphabet
bool isAlphabet(char ch)
{
    if (ch >= 'a' && ch <= 'z')
        return true;

    if (ch >= 'A' && ch <= 'Z')
        return true;

    return false;
}

// function to remove consonants
string removeConsonants(string str)
{
    vector<char> vowels = { 'a', 'e', 'i', 'o', 'u',
                            'A', 'E', 'I', 'O', 'U' };

    unordered_set<char> set;

    set.insert(vowels.begin(), vowels.end());

    for (int i = 0; i < str.length(); i++) {

        if (isAlphabet(str[i])
            && (set.find(str[i]) == set.end())) {
            str.replace(i, 1, "");
            i--;
        }
    }

    // if no vowel is found then return No Vowel
    return str == "" ? "No Vowel" : str;
}

// Driver method
int main()
{
    string str = "GeeeksforGeeks - A Computer Science "
                 "Portal for Geeks";
    cout << removeConsonants(str);
    return 0;
}

Java

// Java program to remove consonants from a String
import java.util.Arrays;
import java.util.List;

class Test {

    // function that returns true
    // if the character is an alphabet
    static boolean isAlphabet(char ch)
    {
        if (ch >= 'a' && ch <= 'z')
            return true;
        if (ch >= 'A' && ch <= 'Z')
            return true;
        return false;
    }

    // function to return the string after
    // removing all the consonants from it
    static String remConsonants(String str)
    {
        Character vowels[]
            = { 'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U' };

        List<Character> al = Arrays.asList(vowels);

        StringBuffer sb = new StringBuffer(str);

        for (int i = 0; i < sb.length(); i++) {

            if (isAlphabet(sb.charAt(i))
                && !al.contains(sb.charAt(i))) {
                sb.replace(i, i + 1, "");
                i--;
            }
        }

        return sb.toString();
    }

    // Driver method to test the above function
    public static void main(String[] args)
    {
        String str
            = "GeeeksforGeeks - A Computer Science Portal for Geeks";

        System.out.println(remConsonants(str));
    }
}

Python3

# Python3 program to remove consonants from a String

# function that returns true
# if the character is an alphabet
def isAlphabet(ch):
    if (ch >= 'a' and ch <= 'z'):
        return True;
    if (ch >= 'A' and ch <= 'Z'):
        return True;
    return False;

# Function to return the string after
# removing all the consonants from it
def remConsonants(str):
    vowels = [ 'a', 'e', 'i', 'o', 'u',  'A', 'E', 'I', 'O', 'U' ]
    sb = "";
    for i in range(len(str)):
        present = False;
        for j in range(len(vowels)):
            if (str[i] == vowels[j]):
                present = True;
                break;
        if (not isAlphabet(str[i]) or present ):
            sb += str[i];
    return sb;

# Driver code
if __name__=='__main__':
    str = "GeeeksforGeeks - A Computer Science Portal for Geeks";
    print(remConsonants(str));

    # This code is contributed by pratham76

C#

// C# program to remove consonants from a String
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

class GFG{

// Function that returns true
// if the character is an alphabet
static bool isAlphabet(char ch)
{
    if (ch >= 'a' && ch <= 'z')
        return true;
    if (ch >= 'A' && ch <= 'Z')
        return true;

    return false;
}

// Function to return the string after
// removing all the consonants from it
static string remConsonants(string str)
{
    char []vowels = { 'a', 'e', 'i', 'o', 'u',
                      'A', 'E', 'I', 'O', 'U' };

    string sb = "";

    for(int i = 0; i < str.Length; i++)
    {
        bool present = false;
        for(int j = 0; j < vowels.Length; j++)
        {
            if (str[i] == vowels[j])
            {
                present = true;
                break;
            }
        }

        if (!isAlphabet(str[i]) || present )
        {
            sb += str[i];
        }
    }
    return sb;
}

// Driver code
public static void Main(string[] args)
{
    string str = "GeeeksforGeeks - A Computer Science Portal for Geeks";

    Console.Write(remConsonants(str));
}
}

// This code is contributed by rutvik_56

Javascript

<script>

      // JavaScript program to remove
      // consonants from a String

      // Function that returns true
      // if the character is an alphabet
      function isAlphabet(ch) {
        if (ch >= "a" && ch <= "z") return true;
        if (ch >= "A" && ch <= "Z") return true;

        return false;
      }

      // Function to return the string after
      // removing all the consonants from it
      function remConsonants(str) {
        var vowels =
        ["a", "e", "i", "o", "u", "A", "E", "I", "O", "U"];

        var sb = "";

        for (var i = 0; i < str.length; i++) {
          var present = false;
          for (var j = 0; j < vowels.length; j++) {
            if (str[i] === vowels[j]) {
              present = true;
              break;
            }
          }

          if (!isAlphabet(str[i]) || present) {
            sb += str[i];
          }
        }
        return sb;
      }

      // Driver code
      var str =
      "GeeeksforGeeks - A Computer Science Portal for Geeks";

      document.write(remConsonants(str));

    </script>

Output

eeeoee - A oue iee oa o ee

Time Complexity: O(N)
Auxiliary Space: O(N)

Below is another program using Regular Expressions in Java

C++

#include <iostream>
#include <string>
#include <regex>

using namespace std;

string remVowel(string str)
{
    // Use regular expression to replace all consonants with
    // empty string
    return regex_replace(str,regex("[BCDFGHJKLMNPQRSTVXZbcdfghjklmnpqrstvxz]"),"");
}

int main()
{
    string str = "GeeeksforGeeks - A Computer Science Portal for Geeks";
    cout << remVowel(str) << endl;

    return 0;
}

Java

// Java program to remove consonants from a String

class Test
{
    static String remVowel(String str)
    {
         return str.replaceAll("[BCDFGHJKLMNPQRSTVXZbcdfghjklmnpqrstvxz]", "");
    }

    // Driver method to test the above function
    public static void main(String[] args)
    {
        String str = "GeeeksforGeeks - A Computer Science Portal for Geeks";

        System.out.println(remVowel(str));
    }
}

Python3

import re
str = 'GeeeksforGeeks - A Computer Science Portal for Geeks'
print(re.sub('[BCDFGHJKLMNPQRSTVXZbcdfghjklmnpqrstvxz]', '', str))

C#

// C# program to remove consonants from a String
using System;
using System.Text.RegularExpressions;

class GFG
{
    static String remVowel(String str)
    {
        return Regex.Replace(str, "[BCDFGHJKLMNPQRSTVXZbcdfghjklmnpqrstvxz]", "");
    }

    // Driver code
    public static void Main()
    {
        String str = "GeeeksforGeeks - A Computer Science Portal for Geeks";

        Console.WriteLine(remVowel(str));
    }
}

// This code is contributed by Rajput-Ji

Javascript

<script>
    // Javascript program to remove consonants from a String


        function remVowel(str)
        {
            return str.replace(new RegExp("[BCDFGHJKLMNPQRSTVXZbcdfghjklmnpqrstvxz]",'g'),"");
        }

        // Driver method to test the above function

        let str = "GeeeksforGeeks - A Computer Science Portal for Geeks";

        document.write(remVowel(str));



    // This code is contributed by Aman Kumar
</script>

Output

eeeoee - A oue iee oa o ee

Time complexity : O(n) where n is the length of string
Auxiliary Space: O(1)