Substring with Maximum Number of Vowels of Given Length (k)

You are given a string of some length (n); the problem is finding a substring of some given length (k) that contains the maximum number of vowels in linear time.

The substring can start from any position in the string, and the vowels can be in any order. If two substrings have the same number of vowels count, the first substring should be returned.

Example 1:

string = 'agfshuekjiylsk'
k = 3
ans = 'hue'
# Here, 'hue' and 'uek' have the same number of vowels = 2. But the answer is 'hue'.

Example 2:

String = 'kwytqpjh'
k = 5
ans = 'Not Found!'
# There is no vowel in the given string. So, an empty string is returned.

Example 3:

string = 'deriikoiuaplo'
k = 5
ans = iikoiu
# The answer has the maximum number of vowels count = 4.

Constraints:

The input will consist of a string and integer k.
All the letters in the input will be in lowercase.
The length of k will be between 1 and len(string)

Python program to find a substring with the maximum number of vowels:

The program can be summarized as follows:

Count the number of vowels in the substring of length k starting from 0: s[0:k]
Check if the count is greater than zero, indicating that the substring contains some vowels.
Store the substring as answer = s[0:k] and make the max_vowel_count = count.
Initialize two variables, i = 0 and j = k.
Check if s[i] is a vowel or not. If yes, then count -= 1
Check if s[j] is a vowel or not. If yes, then count += 1
Check if the count is greater than max_vowel_count or not. If yes, meaning s[i] was a consonant, and s[j] was a vowel.
Update the answer = s[i+1, j+1] and max_vowel_count = count
Repeat steps 5 to 8 until all the letters have been processed.
Return the answer.

# Define a function to find the substring with the maximum number of vowels
# of length k in a given string s
def find_substr(s, k):

    # Initialize an empty string to store the substring
    # with the maximum number of vowels
    ans = "" 
    # Initialize the maximum number of vowels to zero                   
    max_vowel_count = 0
    # Initialize the count of vowels to zero        
    count = 0                   

    # Calculate the number of vowels in the first substring of length k
    for i in s[0:k]:
        if i in 'aeiou':
            count += 1

    # Update the answer and maximum vowel count
    # if the current substring has more vowels than the previous maximum
    if count != 0:
        ans = s[0:k]
        max_vowel_count = count

    # Iterate over all the possible substrings of length k in the given string
    i = 0
    j = k
    while j < len(s):
        # Check if the first character of the ans is a vowel or not
        if s[i] in 'aeiou':
            # If Yes, decrease the vowel count by 1
            count -= 1
        # Check whether the next character of ans is a vowel or not
        if s[j] in 'aeiou':
            # If Yes, increase the vowel count by 1
            count += 1

        # Update the answer and maximum vowel count if
        # the current substring has more vowels than the previous maximum
        if count > max_vowel_count:
            ans = s[i+1:j+1]
            max_vowel_count = count
        
        # Increment i and j for the next iteration
        i += 1
        j += 1
    
    # Return 'No Substring Found!' if no substring with
    # vowels of length k is found
    if ans == "":
        return 'No Substring Found!'
    return ans

# Get necessary inputs from the user
s = input("Enter a string: ")
k = int(input("Enter the length of the substring: "))

# Call the function
output = find_substr(s, k)

# Print the result
print(f"Output: {output}")

Output

Enter a string: agfshuekjiylsk
Enter the length of the substring: 3
Output: hue

Enter a string: kwytpqjz
Enter the length of the substring: 5
Output: No Substring Found!

Time Complexity - O(n): This is because the program iterates over the given string, and n represents the size of the string.

Space Complexity - O(n): No extra space is needed.

C++ program to find a substring with the maximum number of vowels:

#include <iostream>
#include <string>
using namespace std;

// Define a function to find the substring with
// the maximum number of vowels of length k in a given string s
string find_substr(string s, int k)
{

    // Initialize an empty string to store
    // the substring with the maximum number of vowels
    string ans = "";
    // Initialize the maximum number of vowels to zero
    int max_vowel_count = 0;
    // Initialize the count of vowels to zero
    int count = 0;

    // Calculate the count of vowels in the first substring of length k
    for (int i = 0; i < k; i++)
    {
        if (s[i] == 'a' || s[i] == 'e' || s[i] == 'i' || s[i] == 'o' || s[i] == 'u')
        {
            count++;
        }
    }

    // Update the answer and maximum vowel count if
    // the current substring has more vowels than the previous maximum
    if (count != 0)
    {
        ans = s.substr(0, k);
        max_vowel_count = count;
    }

    int j = k;
    // Iterate over all the possible substrings of length k in the given string
    for (int i = 0; j < s.length(); i++, j++)
    {
        // Check if the first character of the ans is a vowel or not
        if (s[i] == 'a' || s[i] == 'e' || s[i] == 'i' || s[i] == 'o' || s[i] == 'u')
        {
            // # If Yes, decrement the vowel count by 1
            count--;
        }
        // Check whether the next character of ans is a vowel or not
        if (s[j] == 'a' || s[j] == 'e' || s[j] == 'i' || s[j] == 'o' || s[j] == 'u')
        {
            // If Yes, increase the vowel count by 1
            count++;
        }
        // Update the answer and maximum vowel count
        // if the current substring has more vowels than the previous maximum
        if (count > max_vowel_count)
        {
            ans = s.substr(i + 1, j - i);
            max_vowel_count = count;
        }
    }

    // Return 'No Substring Found!' if no substring with vowels of length k is found
    if (ans == "")
    {
        return "No Substring Found!";
    }
    return ans;
}

// Main function
int main()
{
    // Define necessary variables
    string s;
    int k;

    // Take inputs from the user
    cout << "Enter a string: ";
    getline(cin, s);
    cout << "Enter the length of the substring: ";
    cin >> k;

    // Call the function
    string output = find_substr(s, k);
    cout << "Output: " << output << endl;
    return 0;
}

Output

Enter a string: deriikoiuaplo
Enter the length of the substring: 5
Output: iikoi

C program to find a substring with the maximum number of vowels:

#include <stdio.h>
#include <string.h>

// Define a function to find the substring with
// the maximum number of vowels of length k in a given string s
char *find_substr(char s[], int k)
{

    // Initialize an empty string to store the substring with the maximum number of vowels
    char *ans = "";
    // Initialize the maximum number of vowels to zero
    int max_vowel_count = 0;
    // Initialize the count of vowels to zero
    int count = 0;

    // Calculate the count of vowels in the first substring of length k
    for (int i = 0; i < k; i++)
    {
        if (s[i] == 'a' || s[i] == 'e' || s[i] == 'i' || s[i] == 'o' || s[i] == 'u')
        {
            count++;
        }
    }

    // Update the answer and maximum vowel count
    // if the current substring has more vowels than the previous maximum
    if (count != 0)
    {
        ans = strndup(s, k);
        max_vowel_count = count;
    }

    // Iterate over all the possible substrings of length k in the given string
    int j = k;
    for (int i = 0; j < strlen(s); i++, j++)
    {
        // Check if the first character of the ans is a vowel or not
        if (s[i] == 'a' || s[i] == 'e' || s[i] == 'i' || s[i] == 'o' || s[i] == 'u')
        {
            // If Yes, decrement the vowel count by 1
            count--;
        }
        // Check whether the next character of ans is a vowel or not
        if (s[j] == 'a' || s[j] == 'e' || s[j] == 'i' || s[j] == 'o' || s[j] == 'u')
        {
            // If Yes, increase the vowel count by 1
            count++;
        }
        // Update the answer and maximum vowel count if
        // the current substring has more vowels than the previous maximum
        if (count > max_vowel_count)
        {
            free(ans);
            ans = strndup(s + i + 1, k);
            max_vowel_count = count;
        }
    }

    // Return 'No Substring Found!' if no substring with vowels of length k is found
    if (strlen(ans) == 0)
    {
        return "No Substring Found!";
    }
    return ans;
}

// Main function
int main()
{
    // Declare necessary variables
    char s[100];
    int k;

    // Take necessary inputs from the user
    printf("Enter a string: ");
    // Use fgets to read the input string with spaces
    fgets(s, 100, stdin);
    // Remove the newline character from the end of the string
    s[strcspn(s, "\n")] = '\0';

    printf("Enter the length of the substring: ");
    scanf("%d", &k);

    // Call the function
    char *output = find_substr(s, k);

    // Print the result
    printf("Output: %s\n", output);
    // Free the dynamically allocated memory
    free(output);
    return 0;
}

Output

Enter a string: usipaotutpsythsuiaonhuaisre
Enter the length of the substring: 7
Output: uiaonhu

Java program to find a substring with the maximum number of vowels:

import java.util.Scanner;

public class Main {
    public static String findSubstring(String s, int k) {
        String ans = "";
        int maxVowelCount = 0, count = 0;

        // Calculate the count of vowels in the first substring of length k
        for (int i = 0; i < k; i++) {
            if (isVowel(s.charAt(i))) {
                count++;
            }
        }

        // Update the answer and maximum vowel count
        // if the current substring has more vowels than the previous maximum
        if (count != 0) {
            ans = s.substring(0, k);
            maxVowelCount = count;
        }

        // Iterate over all the possible substrings of length k in the given string
        for (int i = 1, j = k; j < s.length(); i++, j++) {
            // Check if the first character of the ans is a vowel or not
            if (isVowel(s.charAt(i - 1))) {
                count--;
            }
            // Check whether the next character of ans is a vowel or not
            if (isVowel(s.charAt(j))) {
                count++;
            }
            // Update the answer and maximum vowel count if
            // the current substring has more vowels than the previous maximum
            if (count > maxVowelCount) {
                ans = s.substring(i, j + 1);
                maxVowelCount = count;
            }
        }

        // Return 'No Substring Found!' if no substring with vowels of length k is found
        if (ans.length() == 0) {
            return "No Substring Found!";
        }
        return ans;
    }

    // Helper function to check whether a character is a vowel or not
    private static boolean isVowel(char c) {
        return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
    }

    public static void main(String[] args) {
        // Take necessary inputs from the user
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a string: ");
        String s = scanner.nextLine();
        System.out.print("Enter the length of the substring: ");
        int k = scanner.nextInt();

        // Call the function and print the result
        String output = findSubstring(s, k);
        System.out.println("Output: " + output);
    }
}

Output

Enter a string: aoabdiewbiieazodgagji
Enter the length of the substring: 5
Output: biiea

Next TopicFlatten Binary Tree to Sorted Linked List

← prev next →

For Videos Join Our Youtube Channel: Join Now

Feedback

Send your Feedback to [email protected]

Help Others, Please Share

Learn Latest Tutorials

Splunk

SPSS

Swagger

Transact-SQL

Tumblr

ReactJS

Regex

Reinforcement Learning

R Programming

RxJS

React Native

Python Design Patterns

Python Pillow

Python Turtle

Keras

Preparation

Aptitude

Reasoning

Verbal Ability

Interview Questions

Company Questions

Trending Technologies

Artificial Intelligence

AWS

Selenium

Cloud Computing

Hadoop

ReactJS

Data Science

Angular 7

Blockchain

Git

Machine Learning

DevOps

B.Tech / MCA

DBMS

Data Structures

DAA

Operating System

Computer Network

Compiler Design

Computer Organization

Discrete Mathematics

Ethical Hacking

Computer Graphics

Software Engineering

Web Technology

Cyber Security

Automata

C Programming

C++

Java

.Net

Python

Programs

Control System

Data Mining

Data Warehouse

^{Like/Subscribe us for latest updates or newsletter}

DS Tutorial

DS Array

DS Linked List

DS Stack

DS Queue

DS Tree

DS Graph

DS Searching

DS Sorting

Differences

Misc

DS MCQ

Substring with Maximum Number of Vowels of Given Length (k)

Example 1:

Example 2:

Example 3:

Constraints:

Python program to find a substring with the maximum number of vowels:

C++ program to find a substring with the maximum number of vowels:

C program to find a substring with the maximum number of vowels:

Java program to find a substring with the maximum number of vowels:

Feedback

Help Others, Please Share

Learn Latest Tutorials

Preparation

Trending Technologies

B.Tech / MCA