Python program to sort Palindrome Words in a Sentence

Difficulty Level : Medium
Last Updated : 01 Apr, 2021

Given a string S representing a sentence, the task is to reorder all the palindromic words present in the sentence in sorted order.

Examples:

Input: S = “Please refer to the madam to know the level”
Output: Please level to the madam to know the refer
Explanation: Here “refer”, “madam”, “level” are the palindromic words. Sorting them generates the sequence {“level”, “madam”, “refer”}.
Input: S = “refer to dad”
Output: dad to refer

Approach: Follow the steps below to solve the problem:

Iterate over the characters of the string.
Split the words in the sentence by spaces using split() and store it as a list, say lis.
Store all the palindromic words present in the sentence S in a list, say newlis[].
Sort the list newlis[] using sort() function.
Initialize a pointer, say j = 0.
Traverse the list lis and replace all the palindromic words with newlis[j] and increment j by 1.
Print the updated sentence

Below is the implementation of the above approach:

Python3

# Python implementation of above program
  
# Function to check if a
# string is a palindrome or not
def palindrome(string):
    if(string == string[::-1]):
        return True
    else:
        return False
  
# Function to print the updated sentence
def printSortedPalindromes(sentence):
    
    # Stores palindromic words
    newlist = []
      
    # Stores the words split by spaces
    lis = list(sentence.split())
      
    # Traversing the list
    for i in lis:
        
        # If current word is palindrome
        if(palindrome(i)):
            
            # Update newlist
            newlist.append(i)
  
    # Sort the words in newlist
    newlist.sort()
  
    # Pointer to iterate newlis
    j = 0
      
    # Traverse the list
    for i in range(len(lis)):
        
        # If current word is palindrome
        if(palindrome(lis[i])):
            
            # Replacing word with
            # current word in newlist
            lis[i] = newlist[j]
              
            # Increment j by 1
            j = j + 1
  
    # Print the updated sentence
    for i in lis:
        print(i, end =" ")
  
  
# Driver Code
  
sentence = "please refer to the madam to know the level"
  
printSortedPalindromes(sentence)

Output:

please level to the madam to know the refer

Time Complexity : O(N * logN)
Auxiliary Space : O(N)

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