Sentence Palindrome (Palindrome after removing spaces, dots, .. etc)
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.
Method#1: 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.
Implementation:
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 |
Python3
# 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 else if ( not (s[h] > = 'a' and s[h] < = 'z' )): h - = 1 # If characters are equal else if (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> |
Sentence is palindrome.
Time Complexity: O(N) where N is the length of the sentence
Space Complexity: O(1)
Method#2: String.erase(), reverse method simultaneously
Following are steps for our idea:
- When user input an sentence, it is further passed inside a method which will evaluate the result or the logic part.
- Method uses following logic for evaluating the result:
- It first convert all the latter in sentence to lowercase.
- It uses String.erase() method on sentence to erase the white-space in between the sentence.
- Now it uses the reverse method to reverse the sentence.
- It checked the sentence and reversed sentence and return result.
Below are implementation of above idea.
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 isPalindrome(string str) { // Transforming to lowercase transform(str.begin(), str.end(), str.begin(), :: tolower ); // Removing the white-spaces str.erase( remove (str.begin(), str.end(), ' ' ), str.end()); // Creating the copy to string string s1 = str; string s2 = str; // Reversing the string s1 reverse(s1.begin(), s1.end()); // Evaluating Result return s1 == s2; } // Driver program to test sentencePalindrome() int main() { string str = "Too hot to hoot" ; if (isPalindrome(str)) cout << "Sentence is palindrome." ; else cout << "Sentence is not palindrome." ; return 0; } |
Python
# Python program to find if a sentence is # palindrome # To check sentence is palindrome or not def isPalindrome(s): # Replacing the white-space in string s1 = s.replace( ' ' , '') # converting string to lowercase s1 = s1.lower() # Reversing the string s2 = s1[:: - 1 ]; # Evaluating the result return True if s1 = = s2 else False # Driver program to test sentencePalindrome() s = "Too hot to hoot" if (isPalindrome(s)): print ( "Sentence is palindrome." ) else : print ( "Sentence is not palindrome." ) # This code is contributed by Sachin Bisht |
Javascript
// Javascript program to find if a sentence is // palindrome // To check sentence is palindrome or not function isPalindrome(str) { // Replacing the white-space let s1 = str.split( ' ' ).join( '' ); // Converting string to lower-case s1 = s1.toLowerCase(); // Reversing the string let s2 = s1.split( '' ).reverse().join( '' ); // Evaluating the result return true ? s1 == s2 : false ; } // Driver program to test sentencePallindrome() let str = "Too hot to hoot" ; if ( isPalindrome(str)) console.log( "Sentence is palindrome" ); else console.log( "Sentence is not palindrome" ); //This code is contributed by avanitrachhadiya2155 |
Java
import java.io.*; // Java program to find if a sentence is // palindrome public class GFG { // To check sentence is palindrome or not static boolean sentencePalindrome(String s) { if (s.isEmpty()) // if String s is empty return true return true ; String str = s.toLowerCase(); // convert the whole string into lower case alphabet //remove non-alphanumeric characters // replace the given string with empty string except the pattern [^a-zA-Z0-9] str = str.replaceAll( "[^a-zA-Z0-9]" , "" ); //The reverse() method of StringBuilder is used to reverse the characters in the StringBuilder. StringBuilder revstr = new StringBuilder(str); revstr.reverse(); String rstr = revstr.toString(); if (str.equals(rstr)) //if string and reversed string both are equal return true return true ; return false ; //else return false } // 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" ); } } |
Sentence is palindrome.
Time Complexity: O(N)
Space Complexity: O(N)
Method: #3: Using Stack
Here we are using the stack to reverse the array and then check whether Sentence is palindrome or not.
Java
import java.io.*; import java.util.*; class GFG { static boolean sentencePalindrome(String s) { char [] str = s.toCharArray(); Stack<Character> stack = new Stack<>(); for ( int i = 0 ; i < s.length(); i++){ if (Character.isLetterOrDigit(str[i])) stack.push(str[i]); } String string = "" ; String reverse = "" ; for (Character character : stack) { reverse += Character.toLowerCase(character); } while (!stack.isEmpty()){ string += Character.toLowerCase(stack.pop()); } return string.equals(reverse); } 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" ); } } |
Sentence is palindrome
Time Complexity: O(N)
Space Complexity: O(N)
This article is contributed by nuclode. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Login to comment...