Replace all consonants with nearest vowels in a string

Given a string with lowercase English alphabets. The task is to replace all the consonants in the string with the nearest vowels. If a consonant is near to two vowels then replace it with the one that comes first in English alphabets. 

Note: Vowels already present in the string must be left as it is.

Examples: 

Input : str = "geeksforgeeks"
Output : eeeiueooeeeiu

Input : str = "gfg"
Output : eee

A simple approach is to compare the consonant with vowels to determine the nearest vowel. First, check if the consonant falls between two vowels. If it falls between 2 vowels then find the absolute difference between the ASCII value of consonant with the ASCII value of both vowels. 

Replace it with that vowel, with which the absolute difference is minimum. 
However, if the ASCII code of consonant does not fall between two vowels, then the consonant can be ‘v’, ‘w’, ‘x’, ‘y’, ‘z’. Hence, the answer is ‘u’ in this case.

Below is the implementation of the above approach: 

C++

// C++ program to replace all consonants
// with nearest vowels in a string
#include <bits/stdc++.h>
using namespace std;

// Function to check if a character is
// vowel or not
bool isVowel(char ch)
{
    if (ch != 'a' && ch != 'e' && ch != 'i'
        && ch != 'o' && ch != 'u')
        return false;

    return true;
}

// Function to replace consonant with
// nearest vowels
string replacingConsonants(string s)
{
    for (int i = 0; i < s.length(); i++) {

        // if, string element is vowel,
        // jump to next element
        if (isVowel(s[i]))
            continue;

        // check if consonant lies between two vowels,
        // if it lies, than replace it with nearest vowel
        else {

            if (s[i] > 'a' && s[i] < 'e') {

                // here the absolute difference of
                // ascii value is considered
                if (abs(s[i] - 'a') > abs(s[i] - 'e'))
                    s[i] = 'e';
                else
                    s[i] = 'a';
            }
            else if (s[i] > 'e' && s[i] < 'i') {
                if (abs(s[i] - 'e') > abs(s[i] - 'i'))
                    s[i] = 'i';
                else
                    s[i] = 'e';
            }
            else if (s[i] > 'i' && s[i] < 'o') {
                if (abs(s[i] - 'i') > abs(s[i] - 'o'))
                    s[i] = 'o';
                else
                    s[i] = 'i';
            }
            else if (s[i] > 'o' && s[i] < 'u') {
                if (abs(s[i] - 'o') > abs(s[i] - 'u'))
                    s[i] = 'u';
                else
                    s[i] = 'o';
            }

            // when s[i] is equal to either
            // 'v', 'w', 'x', 'y', 'z'
            else if (s[i] > 'u')
                s[i] = 'u';
        }
    }

    return s;
}

// Driver code
int main()
{
    string s = "geeksforgeeks";

    cout << replacingConsonants(s);

    return 0;
}

Java

// Java program to replace all consonants
// with nearest vowels in a string

import java.util.*;
class Solution{

// Function to check if a character is
// vowel or not
static boolean isVowel(char ch)
{
    if (ch != 'a' && ch != 'e' && ch != 'i'
        && ch != 'o' && ch != 'u')
        return false;

    return true;
}

// Function to replace consonant with
// nearest vowels
static String replacingConsonants(String s)
{
    for (int i = 0; i < s.length(); i++) {

        // if, string element is vowel,
        // jump to next element
        if (isVowel(s.charAt(i)))
            continue;

        // check if consonant lies between two vowels,
        // if it lies, than replace it with nearest vowel
        else {

            if (s.charAt(i) > 'a' && s.charAt(i) < 'e') {

                // here the absolute difference of
                // ascii value is considered
                if (Math.abs(s.charAt(i) - 'a') > Math.abs(s.charAt(i) - 'e'))
                    s = s.substring(0,i)+'e'+s.substring(i+1);
                else
                    s=  s.substring(0,i)+'a'+s.substring(i+1);
            }
            else if (s.charAt(i) > 'e' && s.charAt(i) < 'i') {
                if (Math.abs(s.charAt(i) - 'e') > Math.abs(s.charAt(i) - 'i'))
                    s =  s.substring(0,i)+'i'+s.substring(i+1);
                else
                    s =  s.substring(0,i)+'e'+s.substring(i+1);
            }
            else if (s.charAt(i) > 'i' && s.charAt(i) < 'o') {
                if (Math.abs(s.charAt(i) - 'i') > Math.abs(s.charAt(i) - 'o'))
                    s= s.substring(0,i)+'o'+s.substring(i+1);
                    else
                    s= s.substring(0,i)+'i'+s.substring(i+1);
                }
            else if (s.charAt(i) > 'o' && s.charAt(i) < 'u') {
                if (Math.abs(s.charAt(i) - 'o') > Math.abs(s.charAt(i) - 'u'))
                    s= s.substring(0,i)+'u'+s.substring(i+1);
                else
                    s= s.substring(0,i)+'o'+s.substring(i+1);
            }

            // when s.charAt(i) is equal to either
            // 'v', 'w', 'x', 'y', 'z'
            else if (s.charAt(i) > 'u')
                s =s.substring(0,i)+'u'+s.substring(i+1);
        }
    }

    return s;
}

// Driver code
public static void main(String args[])
{
    String s = "geeksforgeeks";

    System.out.print( replacingConsonants(s));

}

}
//contributed by Arnab Kundu

Python3

# Python3 program to replace all consonants
# with nearest vowels in a string

# Function to check if a
# character is vowel or not
def isVowel(ch):

    if (ch != 'a' and ch != 'e' and ch != 'i'
        and ch != 'o' and ch != 'u'):
        return False

    return True

# Function to replace consonant
# with nearest vowels
def replacingConsonants(s):

    for i in range(0, len(s)):

        # if, string element is vowel,
        # jump to next element
        if isVowel(s[i]):
            continue

        # check if consonant lies between two vowels,
        # if it lies, than replace it with nearest vowel
        else:

            if s[i] > 'a' and s[i] < 'e':

                # here the absolute difference of
                # ascii value is considered
                if (abs(ord(s[i]) - ord('a')) > abs(ord(s[i]) - ord('e'))):
                    s[i] = 'e'
                else:
                    s[i] = 'a'

            elif s[i] > 'e' and s[i] < 'i':
                if (abs(ord(s[i]) - ord('e')) > abs(ord(s[i]) - ord('i'))):
                    s[i] = 'i'
                else:
                    s[i] = 'e'

            elif (s[i] > 'i' and s[i] < 'o'):
                if (abs(ord(s[i]) - ord('i')) > abs(ord(s[i]) - ord('o'))):
                    s[i] = 'o'
                else:
                    s[i] = 'i'

            elif (s[i] > 'o' and s[i] < 'u'):
                if (abs(ord(s[i]) - ord('o')) > abs(ord(s[i]) - ord('u'))):
                    s[i] = 'u'
                else:
                    s[i] = 'o'

            # when s[i] is equal to either
            # 'v', 'w', 'x', 'y', 'z'
            elif (s[i] > 'u'):
                s[i] = 'u'

    return ''.join(s)

# Driver code
if __name__ == "__main__":

    s = "geeksforgeeks"
    print(replacingConsonants(list(s)))

# This code is contributed by Rituraj Jain

C#

// C# program to replace all consonants
// with nearest vowels in a string
using System;
public class Solution{

    // Function to check if a character is
    // vowel or not
    static bool isVowel(char ch)
    {
        if (ch != 'a' && ch != 'e' && ch != 'i'
            && ch != 'o' && ch != 'u')
            return false;

        return true;
    }

    // Function to replace consonant with
    // nearest vowels
    static String replacingConsonants(String s)
    {
        for (int i = 0; i < s.Length; i++) {

            // if, string element is vowel,
            // jump to next element
            if (isVowel(s[i]))
                continue;

            // check if consonant lies between two vowels,
            // if it lies, than replace it with nearest vowel
            else {

                if (s[i] > 'a' && s[i] < 'e') {

                    // here the absolute difference of
                    // ascii value is considered
                    if (Math.Abs(s[i] - 'a') > Math.Abs(s[i] - 'e'))
                        s = s.Substring(0,i)+'e'+s.Substring(i+1);
                    else
                        s=  s.Substring(0,i)+'a'+s.Substring(i+1);
                }
                else if (s[i] > 'e' && s[i] < 'i') {
                    if (Math.Abs(s[i] - 'e') > Math.Abs(s[i] - 'i'))
                        s =  s.Substring(0,i)+'i'+s.Substring(i+1);
                    else
                        s =  s.Substring(0,i)+'e'+s.Substring(i+1);
                }
                else if (s[i] > 'i' && s[i] < 'o') {
                    if (Math.Abs(s[i] - 'i') > Math.Abs(s[i] - 'o'))
                        s= s.Substring(0,i)+'o'+s.Substring(i+1);
                        else
                        s= s.Substring(0,i)+'i'+s.Substring(i+1);
                    }
                else if (s[i] > 'o' && s[i] < 'u') {
                    if (Math.Abs(s[i] - 'o') > Math.Abs(s[i] - 'u'))
                        s= s.Substring(0,i)+'u'+s.Substring(i+1);
                    else
                        s= s.Substring(0,i)+'o'+s.Substring(i+1);
                }

                // when s[i] is equal to either
                // 'v', 'w', 'x', 'y', 'z'
                else if (s[i] > 'u')
                    s =s.Substring(0,i)+'u'+s.Substring(i+1);
            }
        }

        return s;
    }

    // Driver code
    public static void Main()
    {
        String s = "geeksforgeeks";

        Console.WriteLine( replacingConsonants(s));

    }
}

// This code is contributed by PrinciRaj1992

Javascript

<script>
      // JavaScript program to replace all consonants
      // with nearest vowels in a string
      // Function to check if a character is
      // vowel or not
      function isVowel(ch) {
        if (ch !== "a" && ch !== "e" && ch !== "i" && ch !== "o" && ch !== "u")
          return false;

        return true;
      }

      // Function to replace consonant with
      // nearest vowels
      function replacingConsonants(s) {
        for (var i = 0; i < s.length; i++) {
          // if, string element is vowel,
          // jump to next element
          if (isVowel(s[i])) continue;
          // check if consonant lies between two vowels,
          // if it lies, than replace it with nearest vowel
          else {
            if (s[i] > "a" && s[i] < "e") {
              // here the absolute difference of
              // ascii value is considered
              if (
                Math.abs(s[i].charCodeAt(0) - "a".charCodeAt(0)) >
                Math.abs(s[i].charCodeAt(0) - "e".charCodeAt(0))
              )
                s = s.substring(0, i) + "e" + s.substring(i + 1);
              else s = s.substring(0, i) + "a" + s.substring(i + 1);
            } else if (s[i] > "e" && s[i] < "i") {
              if (
                Math.abs(s[i].charCodeAt(0) - "e".charCodeAt(0)) >
                Math.abs(s[i].charCodeAt(0) - "i".charCodeAt(0))
              )
                s = s.substring(0, i) + "i" + s.substring(i + 1);
              else s = s.substring(0, i) + "e" + s.substring(i + 1);
            } else if (s[i] > "i" && s[i] < "o") {
              if (
                Math.abs(s[i].charCodeAt(0) - "i".charCodeAt(0)) >
                Math.abs(s[i].charCodeAt(0) - "o".charCodeAt(0))
              )
                s = s.substring(0, i) + "o" + s.substring(i + 1);
              else s = s.substring(0, i) + "i" + s.substring(i + 1);
            } else if (s[i] > "o" && s[i] < "u") {
              if (
                Math.abs(s[i].charCodeAt(0) - "o".charCodeAt(0)) >
                Math.abs(s[i].charCodeAt(0) - "u".charCodeAt(0))
              )
                s = s.substring(0, i) + "u" + s.substring(i + 1);
              else s = s.substring(0, i) + "o" + s.substring(i + 1);
            }

            // when s[i] is equal to either
            // 'v', 'w', 'x', 'y', 'z'
            else if (s[i] > "u")
              s = s.substring(0, i) + "u" + s.substring(i + 1);
          }
        }

        return s;
      }

      // Driver code

      var s = "geeksforgeeks";
      document.write(replacingConsonants(s));
    </script>

Output

eeeiueooeeeiu

Complexity Analysis:

• Time Complexity: O(n), where n is the size of string s
• Auxiliary Space: O(1)

A better approach is to make an array of size 26 that stores nearest vowel for every character. 

Implementation:

C++

// C++ program to replace all consonants
// with nearest vowels in a string
#include <bits/stdc++.h>
using namespace std;

// Function to replace consonant with
// nearest vowels
string replacingConsonants(string s)
{
    char nVowel[] = "aaaeeeeiiiiioooooouuuuuuuu";
    for (int i = 0; i < s.length(); i++)
        s[i] = nVowel[s[i] - 'a'];
    return s;
}

// Driver code
int main()
{
    string s = "geeksforgeeks";

    cout << replacingConsonants(s);

    return 0;
}

Java

// Java program to replace all consonants
// with nearest vowels in a string
import java.util.*;

class solution
{

// Function to replace consonant with
// nearest vowels
static String replacingConsonants(String s)
{

      String str = "aaaeeeeiiiiioooooouuuuuuuu";
      char[] st = s.toCharArray();
    for (int i = 0; i < s.length(); i++)
    {
       int index = st[i]-'a';
       st[i] = str.charAt(index);
    }
    String str1 = new String(st);
    return str1;
}

// Driver code
public static void main(String arr[])
{
    String s = "geeksforgeeks";

    System.out.println(replacingConsonants(s));

}

}
// This code is contributed by Surendra_Gangwar

Python3

# Python3 program to replace all consonants
# with nearest vowels in a string

# Function to replace consonant with
# nearest vowels
def replacingConsonants(s):

    nVowel = "aaaeeeeiiiiioooooouuuuuuuu"

    for i in range (0, len(s)):
        s = s.replace(s[i], nVowel[ord(s[i]) - 97])

    return s

# Driver code
s = "geeksforgeeks";

print(replacingConsonants(s));

# This code is contributed by
# archana_kumari.

C#

// C# program to replace all consonants
// with nearest vowels in a string
using System;

public class solution{

    // Function to replace consonant with
    // nearest vowels
    static String replacingConsonants(String s)
    {

          String str = "aaaeeeeiiiiioooooouuuuuuuu";
          char[] st = s.ToCharArray();
        for (int i = 0; i < s.Length; i++)
        {
           int index = st[i]-'a';
           st[i] = str[index];
        }
        String str1 = new String(st);
        return str1;
    }

    // Driver code
    public static void Main()
    {
        String s = "geeksforgeeks";

        Console.WriteLine(replacingConsonants(s));

    }

}

// This code is contributed by 29AjayKumar

Javascript

<script>

// Javascript program to replace all consonants
// with nearest vowels in a string

// Function to replace consonant with
// nearest vowels
function replacingConsonants(s)
{
    var nVowel = "aaaeeeeiiiiioooooouuuuuuuu";
    for (var i = 0; i < s.length; i++)
        s[i] = nVowel[s[i].charCodeAt(0) - 'a'.charCodeAt(0)];
    return s.join('');
}

// Driver code
var s = "geeksforgeeks".split('');
document.write( replacingConsonants(s));

</script>

Output

eeeiueooeeeiu

Complexity Analysis:

• Time Complexity: O(n), where n is the size of string s
• Auxiliary Space: O(26)