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

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>

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)

Output:

ava

Time complexity : O(n^2)

Space complexity : O(n)

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.:

C++

// C++ program for the above approach
#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

bool isPalindrome(string s) {
    return s == string(s.rbegin(), s.rend());
}

void largestPalin(vector<string> s) {

    // Taking new list
    vector<string> newlist;

    // Traverse the list
    for (string word : s) {
        if (isPalindrome(word)) {
            newlist.push_back(word);
        }
    }

    // Using sorted() method
    sort(newlist.begin(), newlist.end(), [](string a, string b) { return a.size() < b.size(); });

    // Print last word
    cout << newlist.back() << endl;
}

// Driver Code
int main() {

    // Given string
    string str = "My name is ava and i love Geeksforgeeks";
    vector<string> words;
    string word;

    for (char c : str) {
        if (c == ' ') {
            words.push_back(word);
            word.clear();
        } else {
            word += c;
        }
    }

    if (!word.empty()) {
        words.push_back(word);
    }

    largestPalin(words);

    return 0;
}

// This code is contributed by Prajwal Kandekar

Java

import java.util.ArrayList;
import java.util.Collections;

public class Main {
    // Function to check if a string is a palindrome
    public static boolean isPalindrome(String s)
    {
        return s.equals(
            new StringBuilder(s).reverse().toString());
    }

    // Function to find the largest palindrome in a list of
    // words
    public static void largestPalin(ArrayList<String> s)
    {
        // Create a new list to store all the palindromes
        // found
        ArrayList<String> newlist = new ArrayList<>();

        // Iterate over each word in the input list
        for (String word : s) {
            // Check if the current word is a palindrome
            if (isPalindrome(word)) {
                // If it is, add it to the new list
                newlist.add(word);
            }
        }

        // Sort the new list in ascending order of length
        Collections.sort(newlist,
                         (a, b) -> a.length() - b.length());

        // Print the largest palindrome (last element in the
        // sorted list)
        System.out.println(newlist.get(newlist.size() - 1));
    }

    public static void main(String[] args)
    {
        // Input string to be processed
        String str
            = "My name is ava and i love Geeksforgeeks";
        // Create a list to store all the words in the input
        // string
        ArrayList<String> words = new ArrayList<>();
        // Create a string builder to build each word from
        // the input string
        StringBuilder word = new StringBuilder();

        // Iterate over each character in the input string
        for (char c : str.toCharArray()) {
            // If the current character is a space, the
            // current word is complete
            if (c == ' ') {
                // Add the current word to the list of words
                words.add(word.toString());
                // Reset the string builder to build the
                // next word
                word.setLength(0);
            }
            else {
                // Otherwise, append the current character
                // to the current word
                word.append(c);
            }
        }

        // If there is a word left in the string builder,
        // add it to the list of words
        if (word.length() > 0) {
            words.add(word.toString());
        }

        // Find the largest palindrome in the list of words
        largestPalin(words);
    }
}

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>

C#

// C# program for the above approach
using System;
using System.Collections.Generic;
using System.Linq;

public class Program {
  // Function to check if a string is a palindrome
  public static bool IsPalindrome(string s) {
    return s.Equals(new string(s.Reverse().ToArray()));
  }
  // Function to find the largest palindrome in a list of
  // words
  public static void LargestPalin(List < string > s) {
    // Create a new list to store all the palindromes
    // found
    List < string > newList = new List < string > ();

    // Iterate over each word in the input list
    foreach(string word in s) {
      // Check if the current word is a palindrome
      if (IsPalindrome(word)) {
        // If it is, add it to the new list
        newList.Add(word);
      }
    }

    // Sort the new list in ascending order of length
    newList.Sort((a, b) => a.Length - b.Length);

    // Print the largest palindrome (last element in the
    // sorted list)
    Console.WriteLine(newList[newList.Count - 1]);
  }

  public static void Main(string[] args) {
    // Input string to be processed
    string str = "My name is ava and i love Geeksforgeeks";
    // Create a list to store all the words in the input
    // string
    List < string > words = new List < string > ();
    // Create a string builder to build each word from
    // the input string
    System.Text.StringBuilder word = new System.Text.StringBuilder();

    // Iterate over each character in the input string
    foreach(char c in str) {
      // If the current character is a space, the
      // current word is complete
      if (c == ' ') {
        // Add the current word to the list of words
        words.Add(word.ToString());
        // Reset the string builder to build the
        // next word
        word.Clear();
      } else {
        // Otherwise, append the current character
        // to the current word
        word.Append(c);
      }
    }

    // If there is a word left in the string builder,
    // add it to the list of words
    if (word.Length > 0) {
      words.Add(word.ToString());
    }

    // Find the largest palindrome in the list of words
    LargestPalin(words);
  }
}
// Contributed by adityasharmadev01

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

C++

#include <algorithm>
#include <iostream>
#include <regex>
#include <string>

using namespace std;

bool ispalindrome(string word)
{
    return word == string(word.rbegin(), word.rend());
}

void largestPalin(string s)
{
    // Convert string to vector of words
    regex pattern(R "(\b\w+\b)");
    vector<string> words(
        sregex_token_iterator(s.begin(), s.end(), pattern),
        sregex_token_iterator());

    // Using remove_if() and erase() functions to remove
    // non-palindrome words
    words.erase(remove_if(words.begin(), words.end(),
                          [](string word) {
                              return !ispalindrome(word);
                          }),
                words.end());

    // Using max_element() function to find the word with
    // the maximum length
    auto it = max_element(
        words.begin(), words.end(), [](string a, string b) {
            return a.length() < b.length();
        });

    // Printing the largest palindrome
    cout << *it << endl;
}

int main()
{
    string s = "My name is ava and i love Geeksforgeeks";
    largestPalin(s);
    return 0;
}

Java

// Java program for the above approach
import java.util.ArrayList;
import java.util.List;

public class Main {
    public static boolean isPalindrome(String word)
    {
        return word.equals(
            new StringBuilder(word).reverse().toString());
    }

    public static void largestPalin(String s)
    {
        // Convert string to list of words
        String[] words = s.split("\\W+");
        List<String> palindromeWords = new ArrayList<>();
        // Using filter() function to filter palindrome
        // words
        for (String word : words) {
            if (isPalindrome(word)) {
                palindromeWords.add(word);
            }
        }
        // Using max() function to find the word with the
        // maximum length
        String largestPalindrome
            = palindromeWords.stream()
                  .max((a, b)
                           -> Integer.compare(a.length(),
                                              b.length()))
                  .orElse(null);
        System.out.println(largestPalindrome);
    }

    public static void main(String[] args)
    {
        String s
            = "My name is ava and i love Geeksforgeeks";
        largestPalin(s);
    }
}
// Contributed by adityasha4x71

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)

Javascript

// JavaScript program for above approach
function isPalindrome(word) {
  return word === word.split('').reverse().join('');
}

function largestPalin(s) {
  // Convert string to array of words
  const words = s.match(/\b\w+\b/g);
  // Using filter() method to filter palindrome words
  const palindromeWords = words.filter(isPalindrome);
  // Using reduce() method to find the word with the maximum length
  const largestPalindrome = palindromeWords.reduce((a, b) => a.length >= b.length ? a : b, "");
  console.log(largestPalindrome);
}

// Driver Code
const s = "My name is ava and i love Geeksforgeeks";
largestPalin(s);

// Contributed by adityasha4x71

C#

using System;
using System.Linq;

class Program {
    static bool IsPalindrome(string word)
    {
        return word.SequenceEqual(word.Reverse());
    }

    static string LargestPalin(string s)
    {
        // Convert string to array of words
        var words = s.Split(
            new char[] { ' ' },
            StringSplitOptions.RemoveEmptyEntries);
        // Using LINQ to filter palindrome words
        var palindromeWords = words.Where(IsPalindrome);
        // Using LINQ to find the word with the maximum
        // length
        var largestPalindrome
            = palindromeWords
                  .OrderByDescending(word = > word.Length)
                  .FirstOrDefault();
        return largestPalindrome;
    }

    static void Main(string[] args)
    {
        string s
            = "My name is ava and i love Geeksforgeeks";
        string largestPalindrome = LargestPalin(s);
        Console.WriteLine(largestPalindrome);
    }
}

Output

ava

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