Python program to check if given string is vowel Palindrome

Last Updated : 21 Mar, 2023

Given a string (may contain both vowel and consonant letters), remove all consonants, then check if the resulting string is palindrome or not. Examples:

Input :  abcuhuvmnba
Output : YES
Explanation :
The consonants in the string "abcuhuvmnba"
are removed. Now the string becomes "auua".

Input : xayzuezyax
Output : NO

Input : bkldhgcj
Output : -1

Approach: Remove all the consonants in the string. Check if the vowel string is a palindrome. If it is a palindrome print YES, else print NO. If string contains no vowels, then print -1. Below is the Python implementation:

Python3

# Python program to check if given 
# string is vowel Palindrome 
 
# Function to check if a given string is a vowel 
def vowel(c): 
     
    # creating a list of vowels 
    v = list("aeiou") 
     
    # if the character is a vowel return True 
    if c in v: return True
    return False
 
# Function to check if a vowel 
# string is palindrome 
def palindrome(s): 
     
    # create a empty list 
    v = [] 
     
    # append all vowels into the list 
    for i in s: 
        if vowel(i):v.append(i) 
     
    # if the length of the vowel 
    # string is 0 then print -1 
    if len(v)== 0: print("-1") 
     
    # else check if it is a palindrome 
    else: 
        # create a reversed string 
        x = v[::-1] 
         
        # initialize a flag 
        f = 1
        for i in range(len(x)): 
             
            # if the characters are not the same 
            if x[i]!= v[i]: 
                 
                # set the flag to 0 
                f = 0
                break
                 
        if f == 1: print("YES") 
        else: print("NO") 
         
# Driver Code 
s = 'abcuhuvmnba'
 
# calling the main function 
palindrome(s.strip()) 

Output

YES

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

Approach : Using for loop

Python3

# Python program to check if given
# string is vowel Palindrome
 
s = 'abcuhuvmnba'
vow="aeiou"
x=""
for i in s:
    if i in vow:
        x+=i
if(len(x)==0):
    res=-1
else:
    if(x==x[::-1]):
        res="YES"
    else:
        res="NO"
print(res)

Output

YES

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

Approach: Using regular expressions

Python3

import re
 
def vowel_palindrome(s):
    vowels = re.findall(r'[aeiou]', s)
    if vowels == vowels[::-1]:
        print("YES")
    else:
        print("NO")
 
s = 'abcuhuvmnba'
vowel_palindrome(s)
#This code is contributed by vinay pinjala.

Output

YES

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

Approach: Using reversed function:

This is a Python function called vowel_palindrome_2 that takes a single string as input and checks whether the vowels in the string form a palindrome. Here’s how the code works:

The function uses the re module in Python to find all the vowels in the input string s using the re.findall() function. The regular expression [aeiou] matches any vowel in the input string, and re.findall() returns a list of all the matches found.

The list of vowels found is reversed using the reversed() function and converted to a regular list using the list() function.

The function then checks if the reversed list of vowels is equal to the original list of vowels. If they are equal, it means that the vowels in the input string form a palindrome. If they are not equal, it means that the vowels do not form a palindrome.

Finally, the function prints “YES” if the vowels form a palindrome and “NO” otherwise.

The function is tested with an example input string ‘abcuhuvmnba’ using the vowel_palindrome_2() function.

Python3

import re
def vowel_palindrome_2(s):
    # Using the re module to find all vowels in the input string `s`
    vowels = re.findall(r'[aeiou]', s)
    # Reversing the list of vowels found and checking if it is equal to the original list of vowels
    if list(reversed(vowels)) == vowels:
        print("YES")
    else:
        print("NO")
# Example input string
s = 'abcuhuvmnba'
# Calling the function
vowel_palindrome_2(s)
#This code is contributed by Jyothi pinjala.

Output

YES

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

Approach 5: Using two pointers to compare characters from both ends

Initialize two pointers, one pointing to the start of the string and another to the end of the string.
Traverse the string using the pointers until they meet in the middle:
a. Check if the character at the start pointer is a vowel. If not, move the start pointer to the right.
b. Check if the character at the end pointer is a vowel. If not, move the end pointer to the left.
c. If both characters are vowels, compare them. If they are not equal, print “NO” and exit the function.
If the loop completes without any unequal vowels, print “YES”.

Python3

# Python program to check if given 
# string is vowel Palindrome 
 
# Function to check if a given character is a vowel
def is_vowel(c): 
    # creating a set of vowels 
    vowels = set("aeiou") 
     
    # if the character is a vowel return True 
    return c in vowels
 
# Function to check if a vowel string is palindrome 
def is_vowel_palindrome(s): 
    # initialize pointers to start and end of the string
    start = 0
    end = len(s) - 1
     
    # traverse the string using the pointers until they meet in the middle
    while start <= end:
        # check if the character at the start pointer is a vowel
        if not is_vowel(s[start]):
            start += 1
            continue
         
        # check if the character at the end pointer is a vowel
        if not is_vowel(s[end]):
            end -= 1
            continue
         
        # if both characters are vowels, compare them
        if s[start] != s[end]:
            print("NO")
            return
         
        # move the pointers towards the middle
        start += 1
        end -= 1
     
    print("YES")
 
# Driver Code 
s = 'abcuhuvmnba'
 
# calling the main function 
is_vowel_palindrome(s.strip()) 