Longest substring of vowels

Given a string s of lowercase letters, we need to find the longest substring length that contains (a, e, i, o, u) only. 

Examples : 

Input: s = "geeksforgeeks"
Output: 2
Longest substring is "ee"

Input: s = "theeare"
Output: 3

The idea is to traverse the string and keep track of the current number of vowels in the string. If we see a character that is not a vowel, we reset count to 0. But before resetting we update the max count value which is going to be our result. 

Implementation:

C++

// CPP program to find the
// longest substring of vowels.
#include <bits/stdc++.h>
using namespace std;

bool isVowel(char c)
{
    return (c == 'a' || c == 'e' || c == 'i'
            || c == 'o' || c == 'u');

}

int longestVowel(string s)
{
    int count = 0, res = 0;
    for (int i = 0; i < s.length(); i++)
    {

        // Increment current count
        // if s[i] is vowel
        if (isVowel(s[i]))
        count++;

        else
        {

            // check previous value
            // is greater then or not
            res = max(res, count);

            count = 0;
        }
    }
    return max(res, count);
}

// Driver code
int main()
{
    string s = "theeare";
    cout << longestVowel(s) << endl;
    return 0;
}

Java

// Java program to find the
// longest substring of vowels.
import java.util.*;

class GFG
{

    static boolean isVowel(char c)
    {
        return (c == 'a' || c == 'e' || c == 'i'
                 || c == 'o' || c == 'u');
    }

    static int longestVowel(String str)
    {
        int count = 0, res = 0;
        char[] s = str.toCharArray();

        for (int i = 0; i < s.length; i++)
        {

            // Increment current count
            // if s[i] is vowel
            if (isVowel(s[i]))
            count++;

            else
            {
                // check previous value
                // is greater then or not
                res = Math.max(res, count);

                count = 0;
            }
        }

    return Math.max(res, count);
    }

// Driver code
public static void main (String[] args)
{
    String s = "theeare";
    System.out.println(longestVowel(s));
}
}
// This code is contributed by Mr. Somesh Awasthi

Python3

# Python3 program to find the
# longest substring of vowels.
def isVowel(c):
    return (c == 'a' or c == 'e' or
            c == 'i' or c == 'o' or
            c == 'u')

def longestVowel(s):
    count, res = 0, 0

    for i in range(len(s)):

        # Increment current count
        # if s[i] is vowel
        if (isVowel(s[i])):
            count += 1

        else:

            # check previous value
            # is greater then or not
            res = max(res, count)

            count = 0
    return max(res, count)

# Driver code
if __name__ == "__main__":
    s = "theeare"
    print (longestVowel(s))

# This code is contributed by Chitranayal

C#

// C# program to find the
// longest substring of vowels.
using System;

class GFG
{

    static bool isVowel(char c)
    {
        return (c == 'a' || c == 'e' || c == 'i'
                || c == 'o' || c == 'u');
    }

    static int longestVowel(String str)
    {
        int count = 0, res = 0;
        char []s = str.ToCharArray();

        for (int i = 0; i < s.Length; i++)
        {

            // Increment current count
            // if s[i] is vowel
            if (isVowel(s[i]))
            count++;

            else
            {
                // check previous value
                // is greater then or not
                res = Math.Max(res, count);

                count = 0;
            }
        }

    return Math.Max(res, count);
    }

// Driver code
public static void Main ()
    {
        String s = "theeare";
        Console.Write(longestVowel(s));
    }
}

// This code is contributed by nitin mittal

PHP

<?php
// PHP program to find the
// longest substring of vowels.
function isVowel($c)
{
    return ($c == 'a' || $c == 'e' ||
            $c == 'i' || $c == 'o' ||
            $c == 'u');
}

function longestVowel($s)
{
    $count = 0; $res = 0;
    for ($i = 0; $i < strlen($s); $i++)
    {

        // Increment current count
        // if s[i] is vowel
        if (isVowel($s[$i]))
        $count++;

        else
        {

            // check previous value
            // is greater then or not
            $res = max($res, $count);

            $count = 0;
        }
    }
    return max($res, $count);
}

// Driver code
$s = "theeare";
echo longestVowel($s) ;

// This code is contributed
// by nitin mittal.
?>

Javascript

<script>

// Javascript program to find the
// longest substring of vowels.
function isVowel(c)
{
    return (c == 'a' || c == 'e' ||
            c == 'i' || c == 'o' ||
            c == 'u');
}

function longestVowel(str)
{
    let count = 0, res = 0;
    let s = str.split("");

    for(let i = 0; i < s.length; i++)
    {

        // Increment current count
        // if s[i] is vowel
        if (isVowel(s[i]))
            count++;
        else
        {

            // Check previous value
            // is greater then or not
            res = Math.max(res, count);

            count = 0;
        }
    }
    return Math.max(res, count);
}

// Driver code
let s = "theeare";
document.write(longestVowel(s));

// This code is contributed by avanitrachhadiya2155

</script>

Output

3

Time Complexity: O(n)
Auxiliary Space: O(1)

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