Question

Use a Stack and Queue to check if a string is a palindrome. Assume your method signature is public static boolean isFalindrome (String str)

Answer 1

//Palindrome3.java

import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
import java.util.Stack;

public class Palindrome3 {
    private static boolean isPalindrome(String str){
        int len = str.length();
        char temp;
        int i;
        str = str.toLowerCase();
        Stack<Character> stack = new Stack<Character>();
        Queue<Character> queue = new LinkedList<>();
        for (i = 0; i < len; i++) {
            temp = str.charAt(i);
            if(temp>='a' && temp<='z') {
                stack.push(temp);
                queue.add(temp);
            }
        }
        while(!stack.isEmpty() && !queue.isEmpty()){
            if(stack.pop() != queue.poll()){
                return false;
            }
        }
        return true;
    }

    public static void main(String args[]){
        Scanner scanner = new Scanner(System.in);

        System.out.print("Enter a string: ");
        String str = scanner.nextLine();
        if (isPalindrome(str)) {
            System.out.println(str + " IS a palindrome!");
        } else {
            System.out.println(str + " is NOT a palindrome!");
        }

    }
}

Enter a string: madam madam IS a palindrome! Process finished with exit code 0

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