Reverse vowels in a given string

13 Jul, 2022
Given a string, your task is to reverse only the vowels of string.
Examples: 
Input : hello
Output : holle

Input : hello world
Output : hollo werld
One simple solution is to store all the vowels while scanning the string and placing the vowels in the reverse order in another iteration of string. 
Implementation:
C++
Java
Python3
C#
Javascript
// C++ program to reverse order of vowels#include<bits/stdc++.h>using namespace std; // utility function to check for vowelbool isVowel(char c){    return (c=='a' || c=='A' || c=='e' ||            c=='E' || c=='i' || c=='I' ||            c=='o' || c=='O' || c=='u' ||            c=='U');} // Function to reverse order of vowelsstring reverseVowel(string str){    int j=0;    // Storing the vowels separately    string vowel;    for (int i=0; str[i]!='\0'; i++)        if (isVowel(str[i]))            vowel[j++] = str[i];     // Placing the vowels in the reverse    // order in the string    for (int i=0; str[i]!='\0'; i++)        if (isVowel(str[i]))            str[i] = vowel[--j] ;     return str;} // Driver functionint main(){    string str = "hello world";    cout << reverseVowel(str);    return 0;}
// Java program to reverse order of vowels class GFG { // utility function to check for vowel    static boolean isVowel(char c) {        return (c == 'a' || c == 'A' || c == 'e'                || c == 'E' || c == 'i' || c == 'I'                || c == 'o' || c == 'O' || c == 'u'                || c == 'U');    } // Function to reverse order of vowels    static String reverseVowel(String str1) {        int j = 0;        // Storing the vowels separately        char[] str = str1.toCharArray();        String vowel = "";        for (int i = 0; i < str.length; i++) {            if (isVowel(str[i])) {                j++;                vowel += str[i];            }        }         // Placing the vowels in the reverse        // order in the string        for (int i = 0; i < str.length; i++) {            if (isVowel(str[i])) {                str[i] = vowel.charAt(--j);            }        }         return String.valueOf(str);    } // Driver function    public static void main(String[] args) {        String str = "hello world";        System.out.println(reverseVowel(str));    }} // This code is contributed by princiRaj1992
# Python3 program to reverse order of vowels # utility function to check for voweldef isVowel(c):    if (c == 'a' or c == 'A' or c == 'e' or        c == 'E' or c == 'i' or c == 'I' or        c == 'o' or c == 'O' or c == 'u' or c == 'U'):        return True    return False # Function to reverse order of vowelsdef reverserVowel(string):    j = 0    vowel = [0] * len(string)    string = list(string)     # Storing the vowels separately    for i in range(len(string)):        if isVowel(string[i]):            vowel[j] = string[i]            j += 1     # Placing the vowels in the reverse    # order in the string    for i in range(len(string)):        if isVowel(string[i]):            j -= 1            string[i] = vowel[j]     return ''.join(string) # Driver Codeif __name__ == "__main__":    string = "hello world"    print(reverserVowel(string)) # This code is contributed by# sanjeev2552
// C# program to reverse order of vowelsusing System; class GFG{     // utility function to check for vowel    static bool isVowel(char c)    {        return (c == 'a' || c == 'A' || c == 'e'                || c == 'E' || c == 'i' || c == 'I'                || c == 'o' || c == 'O' || c == 'u'                || c == 'U');    }     // Function to reverse order of vowels    static String reverseVowel(String str1)    {        int j = 0;                 // Storing the vowels separately        char[] str = str1.ToCharArray();        String vowel = "";        for (int i = 0; i < str.Length; i++)        {            if (isVowel(str[i]))            {                j++;                vowel += str[i];            }        }         // Placing the vowels in the reverse        // order in the string        for (int i = 0; i < str.Length; i++)        {            if (isVowel(str[i]))            {                str[i] = vowel[--j];            }        }         return String.Join("",str);    }     // Driver code    public static void Main(String[] args)    {        String str = "hello world";        Console.WriteLine(reverseVowel(str));    }} // This code has been contributed by 29AjayKumar
<script>     // JavaScript program to reverse order of vowels         // utility function to check for vowel    function isVowel(c) {        return (c == 'a' || c == 'A' || c == 'e'                || c == 'E' || c == 'i' || c == 'I'                || c == 'o' || c == 'O' || c == 'u'                || c == 'U');    }       // Function to reverse order of vowels    function reverseVowel(str1) {        let j = 0;        // Storing the vowels separately        let str = str1.split('');        let vowel = "";        for (let i = 0; i < str.length; i++) {            if (isVowel(str[i])) {                j++;                vowel += str[i];            }        }           // Placing the vowels in the reverse        // order in the string        for (let i = 0; i < str.length; i++) {            if (isVowel(str[i])) {                str[i] = vowel[--j];            }        }           return str.join("");    }         let str = "hello world";      document.write(reverseVowel(str));         </script>
hollo werld
Time complexity: O(n) where n = length of string Auxiliary Space: O(v) where v = number of vowels in string
A better solution is to use two pointers scanning from beginning and end of the array respectively and manipulate vowels pointed by these pointers. 
Implementation:
C++
Java
Python3
C#
Javascript
// C++ program to reverse order of vowels#include<bits/stdc++.h>using namespace std; // utility function to check for vowelbool isVowel(char c){    return (c=='a' || c=='A' || c=='e' ||            c=='E' || c=='i' || c=='I' ||            c=='o' || c=='O' || c=='u' ||            c=='U');} // Function to reverse order of vowelsstring reverseVowel(string str){    // Start two indexes from two corners    // and move toward each other    int i = 0;    int j = str.length()-1;    while (i < j)    {        if (!isVowel(str[i]))        {            i++;            continue;        }        if (!isVowel(str[j]))        {            j--;            continue;        }         // swapping        swap(str[i], str[j]);         i++;        j--;    }     return str;} // Driver functionint main(){    string str = "hello world";    cout << reverseVowel(str);    return 0;}
// Java program to reverse order of vowels class GFG { // utility function to check for vowel    static boolean isVowel(char c) {        return (c == 'a' || c == 'A' || c == 'e'                || c == 'E' || c == 'i' || c == 'I'                || c == 'o' || c == 'O' || c == 'u'                || c == 'U');    } // Function to reverse order of vowelsstatic String reverseVowel(String str) {    // Start two indexes from two corners    // and move toward each other    int i = 0;    int j = str.length()-1;    char[] str1 = str.toCharArray();    while (i < j)    {        if (!isVowel(str1[i]))        {            i++;            continue;        }        if (!isVowel(str1[j]))        {            j--;            continue;        }         // swapping        char t = str1[i];        str1[i]= str1[j];        str1[j]= t;                  i++;        j--;    }    String str2 = String.copyValueOf(str1);    return str2;} // Driver function    public static void main(String[] args) {        String str = "hello world";        System.out.println(reverseVowel(str));    }}
# Python3 program to reverse order of vowels # utility function to check for voweldef isVowel(c):    return (c=='a' or c=='A' or c=='e' or            c=='E' or c=='i' or c=='I' or            c=='o' or c=='O' or c=='u' or            c=='U') # Function to reverse order of vowelsdef reverseVowel(str):     # Start two indexes from two corners    # and move toward each other    i = 0    j = len(str) - 1    while (i < j):        if not isVowel(str[i]):            i += 1            continue        if (not isVowel(str[j])):            j -= 1            continue                 # swapping        str[i], str[j] = str[j], str[i]        i += 1        j -= 1    return str # Driver functionif __name__ == "__main__":    str = "hello world"    print(*reverseVowel(list(str)), sep = "") # This code is contributed by SHUBHAMSINGH10
// C# program to reverse order of vowelsusing System; class GFG{     // utility function to check for vowel    static Boolean isVowel(char c)    {        return (c == 'a' || c == 'A' || c == 'e'                || c == 'E' || c == 'i' || c == 'I'                || c == 'o' || c == 'O' || c == 'u'                || c == 'U');    } // Function to reverse order of vowelsstatic String reverseVowel(String str){    // Start two indexes from two corners    // and move toward each other    int i = 0;    int j = str.Length-1;    char[] str1 = str.ToCharArray();    while (i < j)    {        if (!isVowel(str1[i]))        {            i++;            continue;        }        if (!isVowel(str1[j]))        {            j--;            continue;        }         // swapping        char t = str1[i];        str1[i]= str1[j];        str1[j]= t;                  i++;        j--;    }    String str2 = String.Join("",str1);    return str2;} // Driver codepublic static void Main(String[] args){    String str = "hello world";    Console.WriteLine(reverseVowel(str));}} // This code is contributed by Rajput-Ji
<script> // JavaScript program to reverse order of vowels // utility function to check for vowelfunction isVowel(c){    return (c == 'a' || c == 'A' || c == 'e'                || c == 'E' || c == 'i' || c == 'I'                || c == 'o' || c == 'O' || c == 'u'                || c == 'U');} // Function to reverse order of vowelsfunction reverseVowel(str){    // Start two indexes from two corners    // and move toward each other    let i = 0;    let j = str.length-1;    let str1 = str.split("");    while (i < j)    {        if (!isVowel(str1[i]))        {            i++;            continue;        }        if (!isVowel(str1[j]))        {            j--;            continue;        }          // swapping        let t = str1[i];        str1[i]= str1[j];        str1[j]= t;                    i++;        j--;    }    let str2 = (str1).join("");    return str2;} // Driver functionlet str = "hello world";document.write(reverseVowel(str));   // This code is contributed by rag2127 </script>
hollo werld
Time complexity : O(n) where n = length of string Auxiliary Space : O(1)
This article is contributed by Gaurav Ahirwar and Gaurav Miglani. 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. 
princiraj1992
Rajput-Ji
29AjayKumar
sanjeev2552
SHUBHAMSINGH10
vaibhavrabadiya117
rag2127
vowel-consonant
Zoho
Strings
Zoho
Strings
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