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.
C++
// C++ program to reverse order of vowels #include<bits/stdc++.h> using namespace std; // utility function to check for vowel 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 string 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 function int main() { string str = "hello world"; cout << reverseVowel(str); return 0; } |
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Java
// 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 |
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Python3
# Python3 program to reverse order of vowels # utility function to check for vowel def 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 vowels def 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 Code if __name__ == "__main__": string = "hello world" print(reverserVowel(string)) # This code is contributed by # sanjeev2552 |
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C#
// C# program to reverse order of vowels using 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 |
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Output:
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.
C++
// C++ program to reverse order of vowels #include<bits/stdc++.h> using namespace std; // utility function to check for vowel 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 string 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 function int main() { string str = "hello world"; cout << reverseVowel(str); return 0; } |
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Java
// 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 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)); } } |
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Python3
# Python3 program to reverse order of vowels # utility function to check for vowel def 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 vowels def 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 function if __name__ == "__main__": str = "hello world" print(*reverseVowel(list(str)), sep = "") # This code is contributed by SHUBHAMSINGH10 |
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C#
// C# program to reverse order of vowels using 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 vowels static 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 code public static void Main(String[] args) { String str = "hello world"; Console.WriteLine(reverseVowel(str)); } } // This code is contributed by Rajput-Ji |
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Output:
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 contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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