TADM2E 2.38
From Algorithm Wiki
X=n-digit number, y= n-digit number (ABCDEFGHIJKLMN) say
X * y = X * N + X * M0 + X * L00 + X * K000 + .... + X * B000000000000 + X * A0000000000000
i.e. n multiples and n additions i.e O(n).
X=n-digit number, y= n-digit number (ABCDEFGHIJKLMN) say
X * y = X * N + X * M0 + X * L00 + X * K000 + .... + X * B000000000000 + X * A0000000000000
i.e. n multiples and n additions i.e O(n).