Print longest palindrome word in a sentence

Given a string str, the task is to print longest palindrome word present in the string str.
Examples:

Input : Madam Arora teaches Malayalam 
Output: Malayalam 
Explanation: The string contains three palindrome words (i.e., Madam, Arora, Malayalam) but the length of Malayalam is greater than the other two.
Input : Welcome to GeeksforGeeks 
Output : No Palindrome Word 
Explanation:The string does not contain any palindrome word so the output is No Palindrome Word. 

Approach:

• longestPalin() function finds the longest palindrome word by extracting every word of the string and passing it to checkPalin() function. An extra space is added in the original string to extract last word.
• checkPalin() function checks if the word is palindrome. It returns true if word is palindrome else returns false. It makes sure that empty strings are not counted as palindrome as the user may enter more than one spaces in between or at the beginning of the string.

C++

/* C++ program to print longest palindrome
word in a sentence and its length*/
#include <iostream>
#include <algorithm>
#include <string>

using namespace std;

// Function to check if a
// word is palindrome
bool checkPalin(string word)
{
    int n = word.length();

    // making the check case
    // case insensitive
    // word = word.toLowerCase();
    transform(word.begin(), word.end(),
              word.begin(), ::tolower);

    // loop to check palindrome
    for (int i = 0; i < n; i++, n--)
        if (word[i] != word[n - 1])
            return false;

    return true;
}

// Function to find longest
// palindrome word
string longestPalin(string str)
{

    // to check last word for palindrome
    str = str + " ";

    // to store each word
    string longestword = "", word = "";

    int length, length1 = 0;
    for (int i = 0; i < str.length(); i++)
    {
        char ch = str[i];

        // extracting each word
        if (ch != ' ')
            word = word + ch;
        else {
            length = word.length();
            if (checkPalin(word) &&
                       length > length1)
            {
                length1 = length;
                longestword = word;
            }

            word = "";
        }
    }

    return longestword;
}

// Driver code
int main()
{
    string s = "My name is ava and i love"
                         " Geeksforgeeks";

    if (longestPalin(s) == "")
        cout<<"No Palindrome"<<" Word";
    else
        cout<<longestPalin(s);
    return 0;
}

// This code is contributed by Manish
// Shaw (manishshaw1)

Java

/*Java program to print longest palindrome
word in a sentence and its length*/

public class GFG {

    // Function to check if a
    // word is palindrome
    static boolean checkPalin(String word)
    {
        int n = word.length();

        // making the check case
        // case insensitive
        word = word.toLowerCase();

        // loop to check palindrome
        for (int i = 0; i < n; i++, n--)
            if (word.charAt(i) !=
                       word.charAt(n - 1))
                return false;

        return true;
    }

    // Function to find longest
    // palindrome word
    static String longestPalin(String str)
    {
        // to check last word for palindrome
        str = str + " ";

        // to store each word
        String longestword = "", word = "";

        int length, length1 = 0;
        for (int i = 0; i < str.length(); i++)
        {
            char ch = str.charAt(i);

            // extracting each word
            if (ch != ' ')
                word = word + ch;
            else {
                length = word.length();
                if (checkPalin(word) &&
                             length > length1)
                {
                    length1 = length;
                    longestword = word;
                }

                word = "";
            }
        }

        return longestword;
    }

    // Driver code
    public static void main(String args[])
    {
        String s = new String("My name is ava "
                + "and i love Geeksforgeeks");

        if (longestPalin(s) == "")
            System.out.println("No Palindrome"
                            + " Word");
        else
            System.out.println(longestPalin(s));
    }
}

Python3

# Python 3 program to print longest palindrome
# word in a sentence and its length

# Function to check if a word is palindrome
def checkPalin(word):

    n = len(word)

    # making the check case
    # case insensitive
    word = word.lower()

    # loop to check palindrome
    for i in range( n):
        if (word[i] != word[n - 1]):
            return False
        n -= 1

    return True

# Function to find longest
# palindrome word
def longestPalin(str):

    # to check last word for palindrome
    str = str + " "

    # to store each word
    longestword = ""
    word = ""

    length1 = 0
    for i in range(len(str)):
        ch = str[i]

        # extracting each word
        if (ch != ' '):
            word = word + ch
        else :
            length = len(word)
            if (checkPalin(word) and
                length > length1):
                length1 = length
                longestword = word

            word = ""

    return longestword

# Driver code
if __name__ == "__main__":

    s = "My name is ava and i love Geeksforgeeks"

    if (longestPalin(s) == ""):
        print("No Palindrome Word")
    else:
        print(longestPalin(s))

# This code is contributed by ita_c

C#

/* C# program to print longest palindrome
word in a sentence and its length*/
using System;
class GFG
{
    // Function to check if a
    // word is palindrome
    static bool checkPalin(string word)
    {
        int n = word.Length;

        // making the check case
        // case insensitive
        word = word.ToLower();

        // loop to check palindrome
        for (int i = 0; i < n; i++, n--)
            if (word[i] != word[n - 1])
                return false;

        return true;
    }

    // Function to find longest
    // palindrome word
    static string longestPalin(string str)
    {

        // to check last word for palindrome
        str = str + " ";

        // to store each word
        string longestword = "", word = "";

        int length, length1 = 0;
        for (int i = 0; i < str.Length; i++)
        {
            char ch = str[i];

            // extracting each word
            if (ch != ' ')
                word = word + ch;
            else {
                length = word.Length;
                if (checkPalin(word) &&
                        length > length1)
                {
                    length1 = length;
                    longestword = word;
                }

                word = "";
            }
        }

        return longestword;
    }

    // Driver code
    public static void Main()
    {
        string s = "My name is ava and i"
           + " love Geeksforgeeks";

        if (longestPalin(s) == "")
            Console.Write("No Palindrome Word");
        else
            Console.Write(longestPalin(s));
    }
}

// This code is contributed by Manish
// Shaw (manishshaw1)

Javascript

<script>
/*Javascript program to print longest palindrome
word in a sentence and its length*/

    // Function to check if a
    // word is palindrome
    function checkPalin(word)
    {
        let n = word.length;

        // making the check case
        // case insensitive
        word = word.toLowerCase();

        // loop to check palindrome
        for (let i = 0; i < n; i++, n--)
            if (word[i] !=
                       word[n-1])
                return false;

        return true;
    }

    // Function to find longest
    // palindrome word
    function longestPalin(str)
    {
        // to check last word for palindrome
        str = str + " ";

        // to store each word
        let longestword = "", word = "";

        let length, length1 = 0;
        for (let i = 0; i < str.length; i++)
        {
            let ch = str[i];

            // extracting each word
            if (ch != ' ')
                word = word + ch;
            else {
                length = word.length;
                if (checkPalin(word) &&
                             length > length1)
                {
                    length1 = length;
                    longestword = word;
                }

                word = "";
            }
        }

        return longestword;
    }

    // Driver code
    let s="My name is ava "
                + "and i love Geeksforgeeks";
    if (longestPalin(s) == "")
        document.write("No Palindrome"
                            + " Word");
    else
        document.write(longestPalin(s));

    // This code is contributed by rag2127
</script>

Output:

ava

Method #2:Using sorted() method in Python:

• The idea is to split the words of the string into a list .
• Traverse the list and append all palindromic words to new list
• Sort the newlist in increasing order of length of words using the sorted() method.
• Finally, print the last string present in the list.

Below is the implementation of the above approach.:

Python3

# Python3 program for the above approach
def ispalindrome(string):
    if(string == string[::-1]):
        return True
    else:
        return False

def largestPalin(s):

    # Taking new list
    newlist = []

    # Traverse the list
    for i in s:
        if(ispalindrome(i)):
            newlist.append(i)

    # Using sorted() method
    s = sorted(newlist, key=len)

    # Print last word
    print(s[len(s)-1])


# Driver Code
if __name__ == "__main__":

    # Given string
    s = "My name is ava and i love Geeksforgeeks"

    # Convert string to list
    l = list(s.split(" "))

    largestPalin(l)

# This code is contributed by vikkycirus

Javascript

<script>

// JavaScript program for the above approach
function ispalindrome(string){
    let temp = string
    temp = temp.split('').reverse().join('')
    if(string == temp)
        return true
    else
        return false
}

function largestPalin(s){

    // Taking new list
    let newlist = []

    // Traverse the list
    for(let i of s){
        if(ispalindrome(i))
            newlist.push(i)
    }

    // Using sorted() method
    newlist.sort((a,b)=>a.length - b.length)
    s = newlist

    // Print last word
    document.write(s[s.length-1],"</br>")
}


// Driver Code

// Given string
let s = "My name is ava and i love Geeksforgeeks"

// Convert string to list
let l = s.split(" ")

largestPalin(l)

// This code is contributed by shinjanpatra

</script>

Output:

ava

Method #3:Using filter() method in Python:

• First, the string is converted into a list of words using the re module.
• Then the filter function is applied to the list of word to, using ispalindrome function to filter out only the palindrome words.
• After max, the function is applied using the len as key to get a word with max length

Python3

import re

def ispalindrome(word):
    return word == word[::-1]

def largestPalin(s):
    # Convert string to list of words
    words = re.findall(r'\b\w+\b', s)
    # Using filter() function to filter palindrome words
    palindrome_words = filter(ispalindrome, words)
    # Using max() function to find the word with the maximum length
    largest_palindrome = max(palindrome_words, key=len)
    print(largest_palindrome)

# Driver Code
if __name__ == "__main__":
    s = "My name is ava and i love Geeksforgeeks"
    largestPalin(s)

Output

ava

Time complexity:O(n)
Auxiliary Space:O(n)