Python program to check whether the string is Symmetrical or Palindrome

• Difficulty Level : Easy
• Last Updated : 25 Sep, 2021

Given a string. the task is to check if the string is symmetrical and palindrome or not. A string is said to be symmetrical if both the halves of the string are the same and a string is said to be a palindrome string if one half of the string is the reverse of the other half or if a string appears same when read forward or backward.

Example:

Input: khokho
Output:
The entered string is symmetrical
The entered string is not palindrome

Input:amaama
Output:
The entered string is symmetrical
The entered string is palindrome

Approach 1: The approach is very naive. In the case of palindrome, a loop is run to the mid of the string and the first and last characters are matched. If the characters are not similar then the loop breaks and the string is not palindrome otherwise the string is a palindrome. In the case of symmetry, if the string length is even then the string is broken into two halves and the loop is run, checking the characters of the strings of both the half. If the characters are not similar then the loops break and the string is not symmetrical otherwise the string is symmetrical. If the string length is odd then the string is broken into two halves in such a way that the middle element is left unchecked, and the above same step is repeated.

Below is the implementation.

Python3

 # Python program to demonstrate# symmetry and palindrome of the# string  # Function to check whether the# string is palindrome or notdef palindrome(a):      # finding the mid, start    # and last index of the string    mid = (len(a)-1)//2     #you can remove the -1 or you add <= sign in line 21     start = 0                #so that you can compare the middle elements also.    last = len(a)-1    flag = 0     # A loop till the mid of the    # string    while(start <= mid):          # comparing letters from right        # from the letters from left        if (a[start]== a[last]):                         start += 1            last -= 1                     else:            flag = 1            break;                 # Checking the flag variable to    # check if the string is palindrome    # or not    if flag == 0:        print("The entered string is palindrome")    else:        print("The entered string is not palindrome")         # Function to check whether the# string is symmetrical or not       def symmetry(a):         n = len(a)    flag = 0         # Check if the string's length    # is odd or even    if n%2:        mid = n//2 +1    else:        mid = n//2             start1 = 0    start2 = mid         while(start1 < mid and start2 < n):                 if (a[start1]== a[start2]):            start1 = start1 + 1            start2 = start2 + 1        else:            flag = 1            break          # Checking the flag variable to    # check if the string is symmetrical    # or not    if flag == 0:        print("The entered string is symmetrical")    else:        print("The entered string is not symmetrical")         # Driver codestring = 'amaama'palindrome(string)symmetry(string)
Output
The entered string is palindrome
The entered string is symmetrical

Approach 2:

We use slicing in this method.

Python3

 string = 'amaama'half = int(len(string) / 2) if len(string) % 2 == 0:  # even    first_str = string[:half]    second_str = string[half:]else:  # odd    first_str = string[:half]    second_str = string[half+1:] # symmetricif first_str == second_str:    print(string, 'string is symmertical')else:    print(string, 'string is not symmertical') # palindromeif first_str == second_str[::-1]:  # ''.join(reversed(second_str)) [slower]    print(string, 'string is palindrome')else:    print(string, 'string is not palindrome')
Output
amaama string is symmertical
amaama string is palindrome

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