Sort an Array of Strings according to the number of Vowels in them

Given an array arr[] of N strings, the task is to sort these strings according to the numbers of vowels in them.

Examples:

Input: arr[] = { “geeks”, “for”, “coding” } 
Output: for, coding, geeks 
for -> o = 1 vowel 
coding -> o, i = 2 vowels 
geeks -> e, e = 2 vowels

Input: arr[] = { “lmno”, “pqrst”, “aeiou”, “xyz” } 
Output: pqrst, xyz, lmno, aeiou  

Approach: The idea is to store each element with its number of vowels in a vector pair and then sort all the elements of the vector according to the number of vowels stored. Finally, print the strings in order.

Below is the implementation of the above approach:  

C++

// C++ implementation of the approach

#include <bits/stdc++.h>
using namespace std;

// Function to check the Vowel
bool isVowel(char ch)
{
    ch = toupper(ch);
    return (ch == 'A' || ch == 'E'
            || ch == 'I' || ch == 'O'
            || ch == 'U');
}

// Returns count of vowels in str
int countVowels(string str)
{
    int count = 0;
    for (int i = 0; i < str.length(); i++)
        if (isVowel(str[i])) // Check for vowel
            ++count;
    return count;
}

// Function to sort the array according to
// the number of the vowels
void sortArr(string arr[], int n)
{
    // Vector to store the number of vowels
    // with respective elements
    vector<pair<int, string> > vp;

    // Inserting number of vowels
    // with respective strings
    // in the vector pair
    for (int i = 0; i < n; i++) {

        vp.push_back(
            make_pair(
                countVowels(
                    arr[i]),
                arr[i]));
    }

    // Sort the vector, this will sort the pair
    // according to the number of vowels
    sort(vp.begin(), vp.end());

    // Print the sorted vector content
    for (int i = 0; i < vp.size(); i++)
        cout << vp[i].second << " ";
}

// Driver code
int main()
{
    string arr[] = { "lmno", "pqrst",
                     "aeiou", "xyz" };
    int n = sizeof(arr) / sizeof(arr[0]);

    sortArr(arr, n);

    return 0;
}

Java

// Java implementation of the approach
import java.util.*;
import java.lang.*;
import java.io.*;

class GFG{

static class pair
{
    int first;
    String second;

    pair(int first,String second)
    {
        this.first = first;
        this.second = second;
    }
}

// Function to check the Vowel
static boolean isVowel(char ch)
{
    ch = Character.toUpperCase(ch);
    return (ch == 'A' || ch == 'E' ||
            ch == 'I' || ch == 'O' ||
            ch == 'U');
}

// Returns count of vowels in str
static int countVowels(String str)
{
    int count = 0;
    for(int i = 0; i < str.length(); i++)

        // Check for vowel
        if (isVowel(str.charAt(i)))
            ++count;

    return count;
}

// Function to sort the array according to
// the number of the vowels
static void sortArr(String arr[], int n)
{

    // Vector to store the number of vowels
    // with respective elements
    ArrayList<pair> vp = new ArrayList<>();

    // Inserting number of vowels
    // with respective strings
    // in the vector pair
    for(int i = 0; i < n; i++)
    {
        vp.add(new pair(countVowels(arr[i]),
                                    arr[i]));
    }

    // Sort the vector, this will sort the pair
    // according to the number of vowels
    Collections.sort(vp, (a, b) -> a.first - b.first);

    // Print the sorted vector content
    for(int i = 0; i < vp.size(); i++)
        System.out.print(vp.get(i).second + " ");
}

// Driver code
public static void main(String[] args)
{
    String arr[] = { "lmno", "pqrst",
                     "aeiou", "xyz" };
    int n = arr.length;

    sortArr(arr, n);
}
}

// This code is contributed by offbeat

Python3

# Python3 implementation of the approach

# Function to check the Vowel
def isVowel(ch) :

    ch = ch.upper();
    return (ch == 'A' or ch == 'E'or ch == 'I' or
            ch == 'O'or ch == 'U');

# Returns count of vowels in str
def countVowels(string) :

    count = 0;
    for i in range(len(string)) :

        # Check for vowel
        if (isVowel(string[i])) :
            count += 1;

    return count;

# Function to sort the array according to
# the number of the vowels
def sortArr(arr, n) :

    # Vector to store the number of vowels
    # with respective elements
    vp = [];

    # Inserting number of vowels
    # with respective strings
    # in the vector pair
    for i in range(n) :

        vp.append((countVowels(arr[i]),arr[i]));

    # Sort the vector, this will sort the pair
    # according to the number of vowels
    vp.sort()

    # Print the sorted vector content
    for i in range(len(vp)) :
        print(vp[i][1], end= " ");

# Driver code
if __name__ == "__main__" :
    arr = [ "lmno", "pqrst","aeiou", "xyz" ];
    n = len(arr);

    sortArr(arr, n);

# This code is contributed by AnkitRai01

C#

// C# implementation of the approach
using System;
using System.Collections.Generic;
class GFG
{

    // Function to check the Vowel
    static bool isVowel(char ch)
    {
        ch = char.ToUpper(ch);
        return (ch == 'A' || ch == 'E'
                || ch == 'I' || ch == 'O'
                || ch == 'U');
    }

    // Returns count of vowels in str
    static int countVowels(string str)
    {
        int count = 0;
        for (int i = 0; i < str.Length; i++)
            if (isVowel(str[i])) // Check for vowel
                ++count;
        return count;
    }

    // Function to sort the array according to
    // the number of the vowels
    static void sortArr(string[] arr, int n)
    {

        // Vector to store the number of vowels
        // with respective elements
        List<Tuple<int, string>> vp = new List<Tuple<int, string>>();

        // Inserting number of vowels
        // with respective strings
        // in the vector pair
        for (int i = 0; i < n; i++)
        {
            vp.Add(new Tuple<int, string>(countVowels(arr[i]), arr[i]));
        }

        // Sort the vector, this will sort the pair
        // according to the number of vowels
        vp.Sort();

        // Print the sorted vector content
        for (int i = 0; i < vp.Count; i++)
            Console.Write(vp[i].Item2 + " ");
    }

  // Driver code
  static void Main()
  {
    string[] arr = { "lmno", "pqrst",
                     "aeiou", "xyz" };
    int n = arr.Length;
    sortArr(arr, n);
  }
}

// This code is contributed by divyesh072019

Javascript

<script>

    // JavaScript implementation of the approach

    // Function to check the Vowel
    function isVowel(ch)
    {
        ch = ch.toUpperCase();
        return (ch == 'A' || ch == 'E'
                || ch == 'I' || ch == 'O'
                || ch == 'U');
    }

    // Returns count of vowels in str
    function countVowels(str)
    {
        let count = 0;
        for (let i = 0; i < str.length; i++)
            if (isVowel(str[i])) // Check for vowel
                ++count;
        return count;
    }

    // Function to sort the array according to
    // the number of the vowels
    function sortArr(arr, n)
    {

        // Vector to store the number of vowels
        // with respective elements
        let vp = [];

        // Inserting number of vowels
        // with respective strings
        // in the vector pair
        for (let i = 0; i < n; i++)
        {
            vp.push([countVowels(arr[i]), arr[i]]);
        }

        // Sort the vector, this will sort the pair
        // according to the number of vowels
        vp.sort();

        // Print the sorted vector content
        for (let i = 0; i < vp.length; i++)
            document.write(vp[i][1] + " ");
    }

    let arr = [ "lmno", "pqrst", "aeiou", "xyz" ];
    let n = arr.length;
    sortArr(arr, n);

</script>

Output:

pqrst xyz lmno aeiou

Time Complexity: O(N*log N), for sorting the array.
Auxiliary Space: O(N), for storing the string in an extra array.

The approach sorts the input list of strings based on the number of vowels they contain using sorting function

C++

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

// Function to count the number of vowels in a word
int countVowels(string word)
{
    // A string of all vowels
    string vowels = "aeiouAEIOU";
    int count = 0;
    for (int i = 0; i < word.length(); i++) {
        // If the character is a vowel, increment the
        // count
        if (vowels.find(word[i]) != string::npos) {
            count++;
        }
    }
    return count;
}

// Function to sort a vector of strings based on the
// number of vowels in each string
vector<string> sortStrings(vector<string> strings)
{
    // Sort the vector of strings based on the number of
    // vowels in each string
    sort(strings.begin(), strings.end(), [](const string& s1, const string& s2) {
        return countVowels(s1) < countVowels(s2);
    });
    return strings;
}

// Main function
int main()
{
    // Input vector of strings
    vector<string> strings = {"lmno", "pqrst", "aeiou", "xyz"};
    // Sort the vector of strings
    vector<string> sortedStrings = sortStrings(strings);
    // Print the sorted vector of strings
    for (const auto& s : sortedStrings) {
        cout << s << " ";
    }
    cout << endl;
    return 0;
}

Java

import java.util.*;

public class GFG {
    // Function to count the number of vowels in a word
    public static int countVowels(String word)
    {
        // A string of all vowels
        String vowels = "aeiouAEIOU";
        int count = 0;
        for (int i = 0; i < word.length(); i++) {
            // If the character is a vowel, increment the
            // count
            if (vowels.indexOf(word.charAt(i)) != -1) {
                count++;
            }
        }
        return count;
    }

    // Function to sort a list of strings based on the
    // number of vowels in each string
    public static List<String>
    sortStrings(List<String> strings)
    {
        // Sort the list of strings based on the number of
        // vowels in each string
        Collections.sort(strings, new Comparator<String>() {
            @Override
            public int compare(String s1, String s2)
            {
                return countVowels(s1) - countVowels(s2);
            }
        });
        return strings;
    }

    // Main function
    public static void main(String[] args)
    {
        // Input list of strings
        List<String> strings = Arrays.asList(
            "lmno", "pqrst", "aeiou", "xyz");
        // Sort the list of strings
        List<String> sortedStrings = sortStrings(strings);
        // Print the sorted list of strings
        System.out.println(sortedStrings);
    }
}

Python3

# Function to count the number of vowels in a word
def count_vowels(word):
    # A string of all vowels
    vowels = "aeiouAEIOU"
    # Return the count of vowels in the word
    return sum(c in vowels for c in word)

# Function to sort a list of strings based on the number of vowels in each string
def sort_strings(strings):
    # Sort the list of strings based on the number of vowels in each string
    return sorted(strings, key=count_vowels)

# Main function
if __name__ == "__main__":
    # Input list of strings
    strings = ["lmno", "pqrst", "aeiou", "xyz"]
    # Sort the list of strings
    sorted_strings = sort_strings(strings)
    # Print the sorted list of strings
    print(sorted_strings)

C#

using System;
using System.Collections.Generic;
using System.Linq;

public class GFG
{
    // Function to count the number of vowels in a word
    public static int CountVowels(string word)
    {
        // A string of all vowels
        string vowels = "aeiouAEIOU";
        int count = 0;
        for (int i = 0; i < word.Length; i++)
        {
            // If the character is a vowel, increment the
            // count
            if (vowels.IndexOf(word[i]) != -1)
            {
                count++;
            }
        }
        return count;
    }

    // Function to sort a list of strings based on the
    // number of vowels in each string
    public static List<string>
    SortStrings(List<string> strings)
    {
        // Sort the list of strings based on the number of
        // vowels in each string
        strings.Sort((s1, s2) => CountVowels(s1) - CountVowels(s2));
        return strings;
    }

    // Main function
    public static void Main(string[] args)
    {
        // Input list of strings
        List<string> strings = new List<string>
        {
            "lmno", "pqrst", "aeiou", "xyz"
        };
        // Sort the list of strings
        List<string> sortedStrings = SortStrings(strings);
        // Print the sorted list of strings
        Console.WriteLine(string.Join(" ", sortedStrings));
    }
}

Javascript

// Javascript program for the above approach

// Function to count the number of vowels in a word
function count_vowels(word) {
  // A string of all vowels
  const vowels = "aeiouAEIOU";
  // Return the count of vowels in the word
  return Array.from(word).filter(c => vowels.includes(c)).length;
}

// Function to sort a list of strings based on the number of vowels in each string
function sort_strings(strings) {
  // Sort the list of strings based on the number of vowels in each string
  return strings.sort((a, b) => count_vowels(a) - count_vowels(b));
}

// Main function
const strings = ["lmno", "pqrst", "aeiou", "xyz"]; // Input list of strings
const sorted_strings = sort_strings(strings); // Sort the list of strings
console.log(sorted_strings); // Print the sorted list of strings

// This code is contributed by princekumaras

Output

['pqrst', 'xyz', 'lmno', 'aeiou']

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