Question

How to check if two halves of a number are equal in Java

Answer 1

public class HalfCheck {

    // Returns true if the two digit-halves of n are equal
    static boolean halvesEqual(int n) {
        String s = Integer.toString(n);
        int len = s.length();

        if (len % 2 != 0) {
            return false; // cannot split evenly
        }

        int half = len / 2;
        String left  = s.substring(0, half);
        String right = s.substring(half);

        return left.equals(right);
    }

    public static void main(String[] args) {
        int[] testNumbers = {1212, 123123, 45454545, 123, 1213};

        for (int n : testNumbers) {
            System.out.println(
                n + " -> " + (halvesEqual(n) ? "equal halves" : "not equal")
            );
        }
    }
}


/*
run:

1212 -> equal halves
123123 -> equal halves
45454545 -> equal halves
123 -> not equal
1213 -> not equal

*/

 

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