Write a function to check whether an integer is a palindrome without using arrays.

Question

Sigiloso · Accepted Answer

Just reverse the number and compare with the original one. Note, that it actually depends on the radix base, whether the number is a palindrome (in that base) or not.

bool is_palindrome(const unsigned n, const unsigned radix = 10)
{
    if (radix <= 0) return false;
    unsigned x = n;
    unsigned reverse = 0;
    while (x != 0)
    {
        reverse *= radix;
        reverse += x % radix;
        x /= radix;
    }
    // 0 is considered a palindrome here
    // (reads the same way from both sides after all)
    return n == reverse;
}

Utsav · Answer

class practice{
    public static void main(String args[]){
        System.out.println(pal(987789));
    }

    public static boolean pal (int a){
        if(a/10 == 0){
            return true;
        }
        int unit=a%10;
        int d=a;
        int count=0;
        while(d/10>0){
            d=d/10;
            count++;
        }

        if(d%10==unit){
            return pal((a-unit*(int)Math.pow(10.0,count))/10);
        }
        return false;
    }
}

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