Python program to check whether the string is Symmetrical or Palindrome
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:
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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) |
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') |
amaama string is symmertical amaama string is palindrome
