Question

How to find a list of numbers up to a limit that is a palindrome in base 10 and base 2 in JavaScript

Answer 1

// Function to check if a number is a palindrome in a given base
function isPalindrome(num, base) {
    if (base < 2) return false; // Invalid base

    let strnumReversed = '';
    let temp = num;

    // Convert number to string in given base
    do {
        const digit = temp % base;
        strnumReversed += (digit < 10)
            ? String.fromCharCode('0'.charCodeAt(0) + digit)
            : String.fromCharCode('A'.charCodeAt(0) + (digit - 10));
        temp = Math.floor(temp / base);
    } while (temp > 0);

    // Check palindrome
    return strnumReversed === strnumReversed.split('').reverse().join('');
}

const limit = 1000;

console.log("Numbers that are palindromes in both base 10 and base 2:");
for (let i = 1; i <= limit; i++) {
    if (isPalindrome(i, 10) && isPalindrome(i, 2)) {
        process.stdout.write(`${i} (binary: `);

        // Print binary representation
        let binary = '';
        let temp = i;
        do {
            binary += (temp % 2) ? '1' : '0';
            temp = Math.floor(temp / 2);
        } while (temp > 0);

        binary = binary.split('').reverse().join('');
        console.log(`${binary})`);
    }
}



/*
run:

Numbers that are palindromes in both base 10 and base 2:
1 (binary: 1)
3 (binary: 11)
5 (binary: 101)
7 (binary: 111)
9 (binary: 1001)
33 (binary: 100001)
99 (binary: 1100011)
313 (binary: 100111001)
585 (binary: 1001001001)
717 (binary: 1011001101)

*/

 

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