C++ String Exercises: Reverse only the vowels of a given string

Last update on April 11 2025 12:48:24 (UTC/GMT +8 hours)

19. Reverse Only the Vowels in a String

Write a C++ program to reverse only the vowels of a given string.

A vowel is a syllabic speech sound pronounced without any stricture in the vocal tract. Vowels are one of the two principal classes of speech sounds, the other being the consonant.

Example-1:

Input: w3resource

Output: w3resuorce

Example-2:

Input: Python

Output: Python

Example-3:

Input: Hello

Output: Holle

Example-4:

Input: USA

Output: ASU

Sample Solution:

C++ Code:

#include <iostream> // Input/output stream library
#include<algorithm> // Standard library for algorithms such as 'std::swap'
#include <stack>    // Standard library for stack data structure
using namespace std; // Using the standard namespace

// Function to reverse the vowels in a given string
string reverse_vowels(string ostr) {
    vector<int> vec_data; // Vector to store the indices of vowels in the string
    string result_str = ostr; // Initialize result string with the original string

    // Loop through the original string to find the indices of vowels and store them in vec_data
    for(int i = 0; i < ostr.length(); i++) {
        if(ostr[i] == 'A' or ostr[i] == 'E' or ostr[i] == 'I' or ostr[i] == 'O' or ostr[i] == 'U' or ostr[i] == 'a' or ostr[i] == 'e' or ostr[i] == 'i' or ostr[i] == 'o' or ostr[i] == 'u' ) {
            vec_data.push_back(i); // Store the index of the vowel in the vector
        }
    }

    // Reverse the vowels in the result string using the indices stored in vec_data
    for(int i = 0; i < vec_data.size() / 2; i++) {
        swap(result_str[vec_data[i]], result_str[vec_data[vec_data.size() - 1 - i]]); // Swap vowels in the result string
    }

    return result_str; // Return the string with reversed vowels
}

// Main function
int main() {
    // Test cases
    char str1[] = "w3resource";
    cout << "Original string: " << str1;
    cout << "\nAfter reversing the vowels of the said string: " << reverse_vowels(str1);

    char str2[] = "Python";
    cout << "\n\nOriginal string: " << str2;
    cout << "\nAfter reversing the vowels of the said string: " << reverse_vowels(str2);

    char str3[] = "Hello";
    cout << "\n\nOriginal string: " << str3;
    cout << "\nAfter reversing the vowels of the said string: " << reverse_vowels(str3);

    char str4[] = "USA";
    cout << "\n\nOriginal string: " << str4;
    cout << "\nAfter reversing the vowels of the said string: " << reverse_vowels(str4);

    return 0; // Return 0 to indicate successful completion
}

Sample Output:

Original string: w3resource
After reversing the vowels of the said string: w3resuorce

Original string: Python
After reversing the vowels of the said string: Python

Original string: Hello
After reversing the vowels of the said string: Holle

Original string: USA
After reversing the vowels of the said string: ASU

Flowchart:

For more Practice: Solve these Related Problems:

Write a C++ program to reverse only the vowel characters in a string while keeping consonants in their original positions.
Write a C++ program that reads a string, extracts its vowels, reverses them, and then reinserts them into the original string positions.
Write a C++ program to swap vowels in a string by identifying vowel indices and reversing their order.
Write a C++ program that processes a string to reverse the order of its vowels while leaving other characters unchanged.

C++ Code Editor:

Contribute your code and comments through Disqus.

Previous C++ Exercise: Length of the longest valid parentheses substring.

Next C++ Exercise: Length of the longest palindrome in a given string.