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Alternate vowel and consonant string

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  • Difficulty Level : Medium
  • Last Updated : 11 Jul, 2022
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Given a string, rearrange characters of the given string such that the vowels and consonants occupy alternate position. If string can not be rearranged in desired way, print “no such string”. The order of vowels with respect to each other and the order of consonants with respect to each other should be maintained. 
If more than one required strings can be formed, print the lexicographically smaller.

Examples: 

Input : geeks
Output : gekes

Input : onse
Output : nose
There are two possible outcomes
"nose" and "ones".  Since "nose"
is lexicographically smaller, we 
print it.
  1. Count number of vowels and consonants in given string.
  2. If difference between counts is more than one, return “Not Possible”.
  3. If there are more vowels than consonants, print first vowel first and recur for remaining string.
  4. If there are more consonants than vowels, print first consonant first and recur for remaining string.
  5. If counts are same, compare first vowel with first consonant and print the smaller one first.

Implementation:

C++




// C++ implementation of alternate vowel and
// consonant string
#include <bits/stdc++.h>
using namespace std;
 
// 'ch' is vowel or not
bool isVowel(char ch)
{
    if (ch == 'a' || ch == 'e' || ch == 'i' ||
            ch == 'o' || ch =='u')
        return true;
    return false;
}
 
// create alternate vowel and consonant string
// str1[0...l1-1] and str2[start...l2-1]
string createAltStr(string str1, string str2,
                    int start, int l)
{
    string finalStr = "";
 
    // first adding character of vowel/consonant
    // then adding character of consonant/vowel
    for (int i=0, j=start; j<l; i++, j++)
        finalStr = (finalStr + str1.at(i)) + str2.at(j);
    return finalStr;
}
 
// function to find the required
// alternate vowel and consonant string
string findAltStr(string str)
{
    int nv = 0, nc = 0;
    string vstr = "", cstr = "";
    int l = str.size();
    for (int i=0; i<l; i++)
    {
        char ch = str.at(i);
 
        // count vowels and update vowel string
        if (isVowel(ch))
        {
            nv++;
            vstr = vstr + ch;
        }
 
        // count consonants and update consonant
        // string
        else
        {
            nc++;
            cstr = cstr + ch;
        }
    }
 
    // no such string can be formed
    if (abs(nv-nc) >= 2)
        return "no such string";
 
    // remove first character of vowel string
    // then create alternate string with
    // cstr[0...nc-1] and vstr[1...nv-1]
    if (nv > nc)
        return (vstr.at(0) + createAltStr(cstr, vstr, 1, nv));
 
    // remove first character of consonant string
    // then create alternate string with
    // vstr[0...nv-1] and cstr[1...nc-1]
    if (nc > nv)
        return (cstr.at(0) + createAltStr(vstr, cstr, 1, nc));
 
    // if both vowel and consonant
    // strings are of equal length
    // start creating string with consonant
    if (cstr.at(0) < vstr.at(0))
        return createAltStr(cstr, vstr, 0, nv);
 
    // start creating string with vowel
    return createAltStr(vstr, cstr, 0, nc);
}
 
// Driver program to test above
int main()
{
    string str = "geeks";
    cout << findAltStr(str);
    return 0;
}

Java




// Java implementation of alternate vowel and
// consonant string
import java.util.*;
 
class GFG
{
 
// 'ch' is vowel or not
static boolean isVowel(char ch)
{
    if (ch == 'a' || ch == 'e' || ch == 'i' ||
            ch == 'o' || ch =='u')
        return true;
    return false;
}
 
// create alternate vowel and consonant string
// str1[0...l1-1] and str2[start...l2-1]
static String createAltStr(String str1, String str2,
                    int start, int l)
{
    String finalStr = "";
 
    // first adding character of vowel/consonant
    // then adding character of consonant/vowel
    for (int i = 0, j = start; j < l; i++, j++)
        finalStr = (finalStr + str1.charAt(i)) +
                                    str2.charAt(j);
    return finalStr;
}
 
// function to find the required
// alternate vowel and consonant string
static String findAltStr(String str)
{
    int nv = 0, nc = 0;
    String vstr = "", cstr = "";
    int l = str.length();
    for (int i = 0; i < l; i++)
    {
        char ch = str.charAt(i);
 
        // count vowels and update vowel string
        if (isVowel(ch))
        {
            nv++;
            vstr = vstr + ch;
        }
 
        // count consonants and update consonant
        // string
        else
        {
            nc++;
            cstr = cstr + ch;
        }
    }
 
    // no such string can be formed
    if (Math.abs(nv - nc) >= 2)
        return "no such string";
 
    // remove first character of vowel string
    // then create alternate string with
    // cstr[0...nc-1] and vstr[1...nv-1]
    if (nv > nc)
        return (vstr.charAt(0) + createAltStr(cstr, vstr, 1, nv));
 
    // remove first character of consonant string
    // then create alternate string with
    // vstr[0...nv-1] and cstr[1...nc-1]
    if (nc > nv)
        return (cstr.charAt(0) + createAltStr(vstr, cstr, 1, nc));
 
    // if both vowel and consonant
    // strings are of equal length
    // start creating string with consonant
    if (cstr.charAt(0) < vstr.charAt(0))
        return createAltStr(cstr, vstr, 0, nv);
 
    // start creating string with vowel
    return createAltStr(vstr, cstr, 0, nc);
}
 
// Driver code
public static void main(String args[])
{
    String str = "geeks";
    System.out.println(findAltStr(str));
}
}
 
// This code is contributed by
// Shashank_Sharma

Python 3




# Python implementation of alternate vowel
# and consonant string
 
# 'ch' is vowel or not
def isVowel(ch):
    if(ch == 'a' or ch == 'e' or
       ch == 'i' or ch == 'o' or
       ch == 'u'):
        return True
    return False
 
# create alternate vowel and consonant string
# str1[0...l1-1] and str2[start...l2-1]
def createAltStr(str1, str2, start, l):
    finalStr = ""
    i = 0
     
    # first adding character of vowel/consonant
    # then adding character of consonant/vowel
    for j in range(start, l):
        finalStr = (finalStr + str1[i]) + str2[j]
        i + 1
 
    return finalStr
 
# function to find the required
# alternate vowel and consonant string
def findAltStr(str1):
    nv = 0
    nc = 0
    vstr = ""
    cstr = ""
    l = len(str1)
    for i in range(0, l):
         
        # count vowels and update vowel string
        if(isVowel(str1[i])):
            nv += 1
            vstr = vstr + str1[i]
             
        # count consonants and update
        # consonant string
        else:
            nc += 1
            cstr = cstr + str1[i]
             
    # no such string can be formed
    if(abs(nv - nc) >= 2):
        return "no such string"
     
    # remove first character of vowel string
    # then create alternate string with
    # cstr[0...nc-1] and vstr[1...nv-1]
    if(nv > nc):
        return (vstr[0] + createAltStr(cstr, vstr, 1, nv))
     
    # remove first character of consonant string
    # then create alternate string with
    # vstr[0...nv-1] and cstr[1...nc-1]
    if(nc > nv):
        return (cstr[0] + createAltStr(vstr, cstr, 1, nc))
     
    # if both vowel and consonant
    # strings are of equal length
    # start creating string with consonant
    if(cstr[0] < vstr[0]):
        return createAltStr(cstr, vstr, 0, nv)
 
    return createAltStr(vstr, cstr, 0, nc)
         
# Driver Code
if __name__ == "__main__":
    str1 = "geeks"
    print(findAltStr(str1))
 
# This code is contributed by Sairahul099

C#




// C# implementation of alternate vowel and
// consonant string
using System;
 
class GFG
{
 
// 'ch' is vowel or not
static Boolean isVowel(char ch)
{
    if (ch == 'a' || ch == 'e' || ch == 'i' ||
            ch == 'o' || ch =='u')
        return true;
    return false;
}
 
// create alternate vowel and consonant string
// str1[0...l1-1] and str2[start...l2-1]
static String createAltStr(String str1, String str2,
                    int start, int l)
{
    String finalStr = "";
 
    // first adding character of vowel/consonant
    // then adding character of consonant/vowel
    for (int i = 0, j = start; j < l; i++, j++)
        finalStr = (finalStr + str1[i]) +
                                    str2[j];
    return finalStr;
}
 
// function to find the required
// alternate vowel and consonant string
static String findAltStr(String str)
{
    int nv = 0, nc = 0;
    String vstr = "", cstr = "";
    int l = str.Length;
    for (int i = 0; i < l; i++)
    {
        char ch = str[i];
 
        // count vowels and update vowel string
        if (isVowel(ch))
        {
            nv++;
            vstr = vstr + ch;
        }
 
        // count consonants and update consonant
        // string
        else
        {
            nc++;
            cstr = cstr + ch;
        }
    }
 
    // no such string can be formed
    if (Math.Abs(nv - nc) >= 2)
        return "no such string";
 
    // remove first character of vowel string
    // then create alternate string with
    // cstr[0...nc-1] and vstr[1...nv-1]
    if (nv > nc)
        return (vstr[0] + createAltStr(cstr, vstr, 1, nv));
 
    // remove first character of consonant string
    // then create alternate string with
    // vstr[0...nv-1] and cstr[1...nc-1]
    if (nc > nv)
        return (cstr[0] + createAltStr(vstr, cstr, 1, nc));
 
    // if both vowel and consonant
    // strings are of equal length
    // start creating string with consonant
    if (cstr[0] < vstr[0])
        return createAltStr(cstr, vstr, 0, nv);
 
    // start creating string with vowel
    return createAltStr(vstr, cstr, 0, nc);
}
 
// Driver code
public static void Main(String []args)
{
    String str = "geeks";
    Console.WriteLine(findAltStr(str));
}
}
 
// This code is contributed by Princi Singh

Javascript




<script>
 
// JavaScript implementation of alternate vowel and
// consonant string
 
// 'ch' is vowel or not
function isVowel(ch)
{
    if (ch == 'a' || ch == 'e' || ch == 'i' ||
            ch == 'o' || ch =='u')
        return true;
    return false;
}
 
// create alternate vowel and consonant string
// str1[0...l1-1] and str2[start...l2-1]
function createAltStr(str1, str2,start,l)
{
    let finalStr = "";
 
    // first adding character of vowel/consonant
    // then adding character of consonant/vowel
    for (let i=0, j=start; j<l; i++, j++)
        finalStr = (finalStr + str1[i] + str2[j]);
    return finalStr;
}
 
// function to find the required
// alternate vowel and consonant string
function findAltStr(str)
{
    let nv = 0, nc = 0;
    let vstr = "", cstr = "";
    let l = str.length;
    for (let i=0; i<l; i++)
    {
        let ch = str[i];
 
        // count vowels and update vowel string
        if (isVowel(ch))
        {
            nv++;
            vstr = vstr + ch;
        }
 
        // count consonants and update consonant
        // string
        else
        {
            nc++;
            cstr = cstr + ch;
        }
    }
 
    // no such string can be formed
    if (Math.abs(nv-nc) >= 2)
        return "no such string";
 
    // remove first character of vowel string
    // then create alternate string with
    // cstr[0...nc-1] and vstr[1...nv-1]
    if (nv > nc)
        return (vstr[0] + createAltStr(cstr, vstr, 1, nv));
 
    // remove first character of consonant string
    // then create alternate string with
    // vstr[0...nv-1] and cstr[1...nc-1]
    if (nc > nv)
        return (cstr[0] + createAltStr(vstr, cstr, 1, nc));
 
    // if both vowel and consonant
    // strings are of equal length
    // start creating string with consonant
    if (cstr.at(0) < vstr.at(0))
        return createAltStr(cstr, vstr, 0, nv);
 
    // start creating string with vowel
    return createAltStr(vstr, cstr, 0, nc);
}
 
// Driver program to test above
let str = "geeks";
document.write(findAltStr(str));
 
// This code is contributed by Shinjan_Patra
</script>

Output

gekes

Time Complexity: O(n), where ‘n’ the is length of the string
Auxiliary Space: O(n), where ‘n’ is the length of the string. 

This article is contributed by Ayush Jauhari. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. 


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