Question

How to check if stack elements are pairwise consecutive in Java

Answer 1

import java.util.Stack;

public class PairwiseConsecutiveChecker {

    public static boolean arePairwiseConsecutive(Stack<Integer> stack) {
        Stack<Integer> temp = new Stack<>();
        
        // Reverse stack into temp to preserve original order
        while (!stack.isEmpty()) {
            temp.push(stack.pop());
        }

        boolean result = true;

        // Check pairs while restoring original stack
        while (!temp.isEmpty()) {
            int first = temp.pop();
            stack.push(first);  // restore

            if (!temp.isEmpty()) {
                int second = temp.pop();
                stack.push(second);  // restore

                if (Math.abs(first - second) != 1) {
                    result = false;
                }
            }
        }

        return result;
    }

    public static void main(String[] args) {
        Stack<Integer> s = new Stack<>();
        s.push(4);
        s.push(5);
        s.push(9);
        s.push(10);
        s.push(18);
        s.push(19);

        System.out.println(arePairwiseConsecutive(s)); 
        System.out.println(s); 
    }
}



/*
run:

true
[4, 5, 9, 10, 18, 19]

*/

 

70+ SQL courses for beginners and professionals