Kaprekar Number - GeeksforGeeks

Kaprekar Number - GeeksforGeeks
A Kaprekar number is a number whose square when divided into two parts and such that sum of parts is equal to the original number and none of the parts has value 0. (Source : Wiki)
Given a number, the task is to check if it is Kaprekar number or not.

1. Find square of n and count number of digits in square.
2. Split square at different positions and see if sum of two parts in any split becomes equal to n.

bool iskaprekar(int n)

{

    if (n == 1)

       return true;

 

    // Count number of digits in square

    int sq_n = n * n;

    int count_digits = 0;

    while (sq_n)

    {

        count_digits++;

        sq_n /= 10;

    }

 

    sq_n = n*n; // Recompute square as it was changed

 

    // Split the square at different poitns and see if sum

    // of any pair of splitted numbers is equal to n.

    for (int r_digits=1; r_digits<count_digits; r_digits++)

    {

         int eq_parts = pow(10, r_digits);

 

         // To avoid numbers like 10, 100, 1000 (These are not

         // Karprekar numbers

         if (eq_parts == n)

            continue;

 

         // Find sum of current parts and compare with n

         int sum = sq_n/eq_parts + sq_n % eq_parts;

         if (sum == n)

           return true;

    }

 

    // compare with original number

    return false;

}

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