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Sentence Palindrome (Palindrome after removing spaces, dots, .. etc)

  • Difficulty Level : Easy
  • Last Updated : 30 May, 2021

Write a program to check if a sentence is a palindrome or not. You can ignore white spaces and other characters to consider sentences as palindrome.
Examples: 

Input : str = "Too hot to hoot."
Output : Sentence is palindrome.

Input : str = "Abc def ghi jklm."
Output : Sentence is not palindrome.

Note that there may be multiple spaces and/or dots between two words. 

To find if a sentence is palindrome, compare each character from left and right. If they are equal, compare until left and right of string are equal or right becomes less than left. Remember to ignore white spaces and other characters in a string.  

C++




// CPP program to find if a sentence is
// palindrome
#include <bits/stdc++.h>
using namespace std;
  
// To check sentence is palindrome or not
bool sentencePalindrome(string str)
{
    int l = 0, h = str.length() - 1;
  
    // Lowercase string
    for (int i = 0; i <= h; i++)
        str[i] = tolower(str[i]);
  
    // Compares character until they are equal
    while (l <= h) {
  
        // If there is another symbol in left
        // of sentence
        if (!(str[l] >= 'a' && str[l] <= 'z'))
            l++;
  
        // If there is another symbol in right
        // of sentence
        else if (!(str[h] >= 'a' && str[h] <= 'z'))
            h--;
  
        // If characters are equal
        else if (str[l] == str[h])
            l++, h--;
  
        // If characters are not equal then
        // sentence is not palindrome
        else
            return false;
    }
  
    // Returns true if sentence is palindrome
    return true;
}
  
// Driver program to test sentencePalindrome()
int main()
{
    string str = "Too hot to hoot.";
  
    if (sentencePalindrome(str))
        cout << "Sentence is palindrome.";
    else
        cout << "Sentence is not palindrome.";
  
    return 0;
}

Java




// Java program to find if a sentence is
// palindrome
public class GFG
{
    // To check sentence is palindrome or not
    static boolean sentencePalindrome(String str)
    {   
        int l = 0;
        int h = str.length()-1;
         
        // Lowercase string
        str = str.toLowerCase();
         
        // Compares character until they are equal
        while(l <= h)
        {
             
            char getAtl = str.charAt(l);
            char getAth = str.charAt(h);
             
            // If there is another symbol in left
            // of sentence
            if (!(getAtl >= 'a' && getAtl <= 'z'))
                l++;
             
            // If there is another symbol in right
            // of sentence
            else if(!(getAth >= 'a' && getAth <= 'z'))
                h--;
             
            // If characters are equal
            else if( getAtl == getAth)
            {
                l++;
                h--;
            }
             
            // If characters are not equal then
            // sentence is not palindrome
            else
                return false;
        }
         
        // Returns true if sentence is palindrome
        return true;   
    }
     
    // Driver program to test sentencePallindrome()
    public static void main(String[] args)
    {
        String str = "Too hot to hoot.";
        if( sentencePalindrome(str))
          System.out.println("Sentence is palindrome");
        else
          System.out.println("Sentence is not" + " " +
                                         "palindrome");
    }
}
 
//This code is contributed by Sumit Ghosh

Python




# Python program to find if a sentence is
# palindrome
# To check sentence is palindrome or not
def sentencePalindrome(s):
    l, h = 0, len(s) - 1
   
    # Lowercase string
    s = s.lower()
   
    # Compares character until they are equal
    while (l <= h):
   
        # If there is another symbol in left
        # of sentence
        if (not(s[l] >= 'a' and s[l] <= 'z')):
            l += 1
   
        # If there is another symbol in right
        # of sentence
        elif (not(s[h] >= 'a' and s[h] <= 'z')):
            h -= 1
   
        # If characters are equal
        elif (s[l] == s[h]):
            l += 1
            h -= 1
         
        # If characters are not equal then
        # sentence is not palindrome
        else:
            return False
    # Returns true if sentence is palindrome
    return True
   
# Driver program to test sentencePalindrome()
s = "Too hot to hoot."
if (sentencePalindrome(s)):
    print "Sentence is palindrome."
else:
    print "Sentence is not palindrome."
 
# This code is contributed by Sachin Bisht

C#




// C# program to find if a
// sentence is palindrome
using System;
 
public class GFG
{
     
    // To check sentence is
    // palindrome or not
    static bool sentencePalindrome(String str)
    {
        int l = 0;
        int h = str.Length - 1;
         
        // Lowercase string
        str = str.ToLower();
         
        // Compares character until
        // they are equal
        while(l <= h)
        {
             
            char getAtl = str[l];
            char getAth = str[h];
             
            // If there is another symbol
            // in left of sentence
            if (!(getAtl >= 'a' &&
                  getAtl <= 'z'))
                l++;
             
            // If there is another symbol 
            // in right of sentence
            else if(! (getAth >= 'a' &&
                       getAth <= 'z'))
                h--;
             
            // If characters are equal
            else if( getAtl == getAth)
            {
                l++;
                h--;
            }
             
            // If characters are not equal then
            // sentence is not palindrome
            else
                return false;
        }
         
        // Returns true if sentence
        // is palindrome
        return true;
    }
     
    // Driver Code
    public static void Main()
    {
        String str = "Too hot to hoot.";
        if( sentencePalindrome(str))
        Console.Write("Sentence is palindrome");
        else
        Console.Write("Sentence is not" + " " +
                                     "palindrome");
    }
}
 
// This code is contributed by Nitin Mittal.

PHP




<?php
// PHP program to find if a sentence is
// palindrome
   
// To check sentence is palindrome or not
function sentencePalindrome($str)
{
    $l = 0;
    $h = strlen($str)-1;
   
    // Lowercase string
    for ($i = 0; $i < $h; $i++)
        $str[$i] = strtolower($str[$i]);
   
    // Compares character until they are equal
    while ($l <= $h) {
   
        // If there is another symbol in left
        // of sentence
        if (!($str[$l] >= 'a' && $str[$l] <= 'z'))
            $l++;
   
        // If there is another symbol in right
        // of sentence
        else if (!($str[$h] >= 'a' && $str[$h] <= 'z'))
            $h--;
   
        // If characters are equal
        else if ($str[$l] == $str[$h])
        {
             $l++;
            $h--;
        }
   
        // If characters are not equal then
        // sentence is not palindrome
        else
            return false;
    }
   
    // Returns true if sentence is palindrome
    return true;
}
   
// Driver program to test sentencePalindrome()
 
$str = "Too hot to hoot.";
 
if (sentencePalindrome($str))
    echo "Sentence is palindrome.";
else
    echo "Sentence is not palindrome.";
 
return 0;
?>

Javascript




<script>
// Javascript program to find if a sentence is
// palindrome
     
    // To check sentence is palindrome or not
    function sentencePalindrome(str)
    {
        let l = 0;
        let h = str.length-1;
          
        // Lowercase string
        str = str.toLowerCase();
          
        // Compares character until they are equal
        while(l <= h)
        {
              
            let getAtl = str[l];
            let getAth = str[h];
              
            // If there is another symbol in left
            // of sentence
            if (!(getAtl >= 'a' && getAtl <= 'z'))
                l++;
              
            // If there is another symbol in right
            // of sentence
            else if(!(getAth >= 'a' && getAth <= 'z'))
                h--;
              
            // If characters are equal
            else if( getAtl == getAth)
            {
                l++;
                h--;
            }
              
            // If characters are not equal then
            // sentence is not palindrome
            else
                return false;
        }
          
        // Returns true if sentence is palindrome
        return true;  
    }
     
    // Driver program to test sentencePallindrome()
    let str = "Too hot to hoot.";
    if( sentencePalindrome(str))
        document.write("Sentence is palindrome");
    else
        document.write("Sentence is not" + " " +
                                         "palindrome");
     
     
    //This code is contributed by avanitrachhadiya2155
     
</script>

Output: 

Sentence is palindrome.

Time Complexity: O(N) where N is the length of the sentence
Space Complexity: O(1) 



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