// The main function that multiplies two bit strings X and Y and returns
// result as long integer
long int multiplyBitStrings(string X, string Y)
{
//length
int length = (X.length()>X.length()) ? X.length() : X.length();
// Base cases
if (length == 0) return 0;
if (length == 1) return (a[0] - '0')*(b[0] - '0');
// Divide and Conquer
int fh = length/2; // First half of string, floor(n/2)
int sh = (length-fh); // Second half of string, ceil(n/2)
// Find the first half and second half of first string.
string a1 = X.substr(0, fh);
string a2 = X.substr(fh, sh);
// Find the first half and second half of second string
string b1 = Y.substr(0, fh);
string b2 = Y.substr(fh, sh);
// Recursively calculate the three products of inputs of size n/2
long int P1 = multiplyBitStrings(a1, b1);
long int P2 = multiplyBitStrings(a2, b2);
long int P3 = multiplyBitStrings(addBitStrings(a1, a2), addBitStrings(b1, b2));
// Combine the three products to get the final result.
return P1*(1<<(2*sh)) + (P3 - P1 - P2)*(1<<sh) + P2;
}
int main()
{
char n1[100] = "10";
char n2[100] = "1";
char *sum = addBitStrings(n1,n2);
puts(sum);
return 0;
}
