Print reverse string after removing vowels

Given a string s, print reverse of string and remove the characters from the reversed string where there are vowels in the original string. 

Examples:

Input : geeksforgeeks
Output : segrfseg
Explanation :
Reversed string is skeegrofskeeg, removing characters 
from indexes 1, 2, 6, 9 & 10 (0 based indexing),
we get segrfseg .

Input :duck
Output :kud

A simple solution is to first reverse the string, then traverse the reversed string and remove vowels.

An efficient solution is to do both tasks in one traversal. 
Create an empty string r and traverse the original string s and assign the value to the string r. Check whether, at that index, the original string contains a consonant or not. If yes then print the element at that index from string r.

Basic implementation of the above approach : 

C++

// CPP Program for removing characters
// from reversed string where vowels are
// present in original string
#include <bits/stdc++.h>
using namespace std;

// Function for replacing the string
void replaceOriginal(string s, int n)
{
    // initialize a string of length n
    string r(n, ' ');

    // Traverse through all characters of string
    for (int i = 0; i < n; i++) {

        // assign the value to string r
        // from last index of string s
        r[i] = s[n - 1 - i];

        // if s[i] is a consonant then
        // print r[i]
        if (s[i] != 'a' && s[i] != 'e' && s[i] != 'i'
            && s[i] != 'o' && s[i] != 'u') {
            cout << r[i];
        }
    }
    cout << endl;
}

// Driver function
int main()
{
    string s = "geeksforgeeks";
    int n = s.length();
    replaceOriginal(s, n);

    return 0;
}

Java

// Java Program for removing characters
// from reversed string where vowels are
// present in original string
class GFG {

// Function for replacing the string
    static void replaceOriginal(String s, int n) {
        // initialize a string of length n
        char r[] = new char[n];

        // Traverse through all characters of string
        for (int i = 0; i < n; i++) {

            // assign the value to string r
            // from last index of string s
            r[i] = s.charAt(n - 1 - i);

            // if s[i] is a consonant then
            // print r[i]
            if (s.charAt(i) != 'a' && s.charAt(i) != 'e' && s.charAt(i) != 'i'
                    && s.charAt(i) != 'o' && s.charAt(i) != 'u') {
                System.out.print(r[i]);
            }
        }
        System.out.println("");
    }

// Driver function
    public static void main(String[] args) {
        String s = "geeksforgeeks";
        int n = s.length();
        replaceOriginal(s, n);
    }
}

// This code is contributed by princiRaj1992

Python3

# Python3 Program for removing characters
# from reversed string where vowels are
# present in original string

# Function for replacing the string
def replaceOriginal(s, n):

    # initialize a string of length n
    r = [' '] * n

    # Traverse through all characters of string
    for i in range(n):

        # assign the value to string r
        # from last index of string s
        r[i] = s[n - 1 - i]

        # if s[i] is a consonant then
        # print r[i]
        if (s[i] != 'a' and s[i] != 'e' and
            s[i] != 'i' and s[i] != 'o' and
            s[i] != 'u'):
            print(r[i], end = "")
    print()

# Driver Code
if __name__ == "__main__":
    s = "geeksforgeeks"
    n = len(s)
    replaceOriginal(s, n)

# This code is contributed by
# sanjeev2552

C#

// C# Program for removing characters
// from reversed string where vowels are
// present in original string
using System;

class GFG
{

    // Function for replacing the string
    static void replaceOriginal(String s, int n)
    {
        // initialize a string of length n
        char []r = new char[n];

        // Traverse through all characters of string
        for (int i = 0; i < n; i++)
        {

            // assign the value to string r
            // from last index of string s
            r[i] = s[n - 1 - i];

            // if s[i] is a consonant then
            // print r[i]
            if (s[i] != 'a' && s[i] != 'e' && s[i] != 'i'
                    && s[i] != 'o' && s[i] != 'u')
            {
                Console.Write(r[i]);
            }
        }
        Console.WriteLine("");
    }

    // Driver code
    public static void Main(String[] args)
    {
        String s = "geeksforgeeks";
        int n = s.Length;
        replaceOriginal(s, n);
    }
}

// This code is contributed by Rajput-JI

Javascript

<script>

// JavaScript Program for removing characters
// from reversed string where vowels are
// present in original string
// Function for replacing the string
function replaceOriginal(s, n)
{

        // initialize a string of length n
        var r = new Array(n);

        // Traverse through all characters of string
        for (var i = 0; i < n; i++) {

            // assign the value to string r
            // from last index of string s
            r[i] = s.charAt(n - 1 - i);

            // if s[i] is a consonant then
            // print r[i]
            if (s.charAt(i) != 'a' && s.charAt(i) != 'e' && s.charAt(i) != 'i'
                    && s.charAt(i) != 'o' && s.charAt(i) != 'u') {
                document.write(r[i]);
            }
        }
        document.write("");
    }

// Driver function
var s = "geeksforgeeks";
var n = s.length;
replaceOriginal(s, n);

// This code is contributed by shivanisinghss2110

</script>

Output

segrfseg

Complexity Analysis:

• Time complexity : O(n) 
• Auxiliary Space : O(n)