Python program to check whether number formed by combining all elements of the array is palindrome

Difficulty Level : Easy
Last Updated : 24 Feb, 2021

Given an array arr[], the task is to combine all the elements in the array sequentially and check if it is a palindrome.

Examples:

Input: arr[] ={1 , 69 , 54 , 45 , 96 , 1}
Output: palindrome
Explaination: The number formed by combining all the elements is “1695445961” which is a palindrome

Input: arr[] ={2 , 73 , 95 , 59 , 96 , 2}
Output: not palindrome
Explaination: The number formed by combining all the elements is “2739559962” which is not a palindrome

Method 1: Using map() and join()

Convert each element of the list to a string using map() function.
Join the list using join() function.
Check if it is a palindrome.
If yes then print palindrome.
If no print, not a palindrome.

Below is the implementation of the above approach:

Python3

# function to check palindrome
def checkPalindrome(string):
    
    # reverse the string
    rev = string[::-1]
      
    # checking if string is equal to reverse
    if(string == rev):
        return True
    else:
        return False
  
# function to convert list to single number string
def joinArray(lis):
    
    # convert the elements of list to string
    lis = list(map(str, lis))
      
    # converting list to string
    number = ''.join(lis)
      
    # checking if it is palindrome
    if(checkPalindrome(number)):
        return True
    else:
        return False
  
# Driver code
lis = [1, 76, 39, 93, 67, 1]
if(joinArray(lis)):
    print("Palindrome")
else:
    print("not Palindrome")

Output:

Palindrome

Time Complexity: O(n)

Method 2: Using type casting and string concatenation

Take an empty string say str.
Traverse through the list and convert each element to string using type casting
Add this to str using string concatenation
Check if str is a palindrome

Below is the implementation of the above approach:

Python3

# function to check palindrome
def checkPalindrome(string):
    
    # reverse the string
    rev = string[::-1]
      
    # checking if string is equal to reverse
    if(string == rev):
        return True
    else:
        return False
  
# function to convert list to single number string
def joinArray(lis):
    
    # defining empty string as number
    number = ""
      
    # convert the elements of list to string using type conversion
    for i in lis:
        
        # converting to string
        i = str(i)
          
        # concat this to string
        number = number + i
  
    # checking if it is palindrome
    if(checkPalindrome(number)):
        return True
    else:
        return False
  
# Driver code
lis = [1, 76, 39, 93, 67, 1]
  
if(joinArray(lis)):
    print("Palindrome")
else:
    print("not Palindrome")