Find Whether Given String is palindrome or Not.

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Objective : Write an algorithm to find Whether Given String is palindrome or Not.

Input:  A String,

Output: true or false on whether string is palindrome or not

Approach:

  • Use recursive approach
  • Compare first and last characters if they are not same- return false
  • If they are same make, remove the first and last characters and make a recursive call. 

Example:

Jain niaJ => compare ‘J’ with ‘J’ =>returns true

ain nia => compare ‘a’ with ‘a’ =>returns true

in ni => compare ‘i’ with ‘i’ =>returns true

n n => compare ‘n’ with ‘n’ =>returns true

string length <2 => returns true

Complete Code:


//Use recursive approach
//Compare first and last characters if they are not same- return false
//If they are same make, remove the first and last characters and make a recursive call.
public class Palindrome {
public Boolean isPalindrome(String strX) {
if (strX.length() < 2)
return true;
if (strX.charAt(0) == strX.charAt(strX.length() – 1)) {
return isPalindrome(strX.substring(1, strX.length() – 1));
} else
return false;
}
public static void main(String args[]) {
String S1 = "Sumit";
String S2 = "SumuS";
String S3 = "ABCDEFGHGFEDCBA";
String S4 = "Jain niaJ";
String S5 = "JasasddfwfcsJ";
Palindrome p = new Palindrome();
System.out.println("Is " + S1 + " Palindrome ??? :"
+ p.isPalindrome(S1));
System.out.println("Is " + S2 + " Palindrome ??? :"
+ p.isPalindrome(S2));
System.out.println("Is " + S3 + " Palindrome ??? :"
+ p.isPalindrome(S3));
System.out.println("Is " + S4 + " Palindrome ??? :"
+ p.isPalindrome(S4));
System.out.println("Is " + S5 + " Palindrome ??? :"
+ p.isPalindrome(S5));
}
}

view raw

Palindrome.java

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Output:

Is Sumit Palindrome ??? :false
Is SumuS Palindrome ??? :true
Is ABCDEFGHGFEDCBA Palindrome ??? :true
Is Jain niaJ Palindrome ??? :true
Is SumuaS Palindrome ??? :false

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