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
Explanation: 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
Explanation: 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 palindromedef 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 stringdef 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 codelis = [1, 76, 39, 93, 67, 1]if(joinArray(lis)): print("Palindrome")else: print("not Palindrome") |
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 palindromedef 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 stringdef 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 codelis = [1, 76, 39, 93, 67, 1]if(joinArray(lis)): print("Palindrome")else: print("not Palindrome") |
Palindrome
Method 3 : Using str(),list(),extend(),join() and reverse() methods
Python3
lis = [1, 76, 39, 93, 67, 1]s = ""for i in lis: s += str(i)x = list(s)y = []y.extend(x)x.reverse()if(x == y): print("Palindrome")else: print("not Palindrome") |
Palindrome
Method 4 : Using reduce():
Algorithm:
- Import the “reduce” function from the “functools” module.
- Create a list of integers “lst”.
- Use the “reduce” function to concatenate all the integers in the list into a single string “s”.
- Check whether the string “s” is equal to its reverse.
- If “s” is equal to its reverse, print “Palindrome”; otherwise, print “Not Palindrome”.
Python3
from functools import reducelst = [1, 76, 39, 93, 67, 1]# concatenate all numbers into a single strings = reduce(lambda x, y: str(x) + str(y), lst)# compare string with its reverseif s == s[::-1]: print("Palindrome")else: print("Not Palindrome") #This code is contributed by Jyothi Pinjala. |
Palindrome
Time complexity: O(n), where n is the number of integers in the list “lst”. This is because the reduce function takes O(n) time to concatenate all the integers into a single string, and checking whether the string is equal to its reverse takes O(n/2) time.
Auxiliary Space: O(n), where n is the number of integers in the list “lst”. This is because the reduce function creates a new string of length n by concatenating all the integers in the list.
