#include #include #include class BigInteger { public: BigInteger() : m_Data( "0" ) {} template::value>::type* = nullptr> // Disallows BigInteger n( 5.5 ) but allows BigInteger n( 5 ) BigInteger( T n ) : m_Data( std::to_string( std::abs( n ) ) ) {} BigInteger( const std::string& s ) : m_Data( s.empty() ? "0" : s.substr( std::min( s.find_first_not_of( '0' ), s.size() - 1 ) ) ) // Removes leading 0s {} BigInteger( const BigInteger& o ) : m_Data( o.m_Data ) {} BigInteger& operator=( const BigInteger& o ) { if( &o != this ) { m_Data = o.m_Data; } return *this; } static BigInteger add( const BigInteger& lhs, const BigInteger& rhs ) { BigInteger r; r.m_Data.clear(); // Cause of the default "0" const BigInteger& shortest = lhs.m_Data.size() > rhs.m_Data.size() ? rhs : lhs; const BigInteger& longest = lhs.m_Data.size() > rhs.m_Data.size() ? lhs : rhs; bool carry = false; size_t i = 0; // Need the index later, so declare here instead of in the loop // Handle the short part first. e.g. 12141 + 99 => 41 + 99 => 40 + carry for( ; i < shortest.m_Data.size(); ++i ) { char lhsdigit = lhs.m_Data[ lhs.m_Data.size() - i - 1 ] - '0'; // Go right-to-left char rhsdigit = rhs.m_Data[ rhs.m_Data.size() - i - 1 ] - '0'; char number = lhsdigit + rhsdigit + carry; carry = false; if( number > 9 ) { number -= 10; carry = true; } r.m_Data += number + '0'; } // Add the rest of the string to the end and handle any additional carries. e.g. 121 + 40 + carry => 12240 for( ; i < longest.m_Data.size(); ++i ) { char lhsdigit = longest.m_Data[ longest.m_Data.size() - i - 1 ] - '0'; char number = lhsdigit + carry; carry = false; if( number > 9 ) { number -= 10; carry = true; } r.m_Data += number + '0'; } // Check if there is still a carry remaining e.g. 999 + 1 => 1000 instead of 000 if( carry ) r.m_Data += "1"; std::reverse( r.m_Data.begin(), r.m_Data.end() ); return r; } friend std::ostream& operator<<( std::ostream& os, const BigInteger& o ) { return os << o.m_Data; } friend BigInteger operator+( const BigInteger& lhs, const BigInteger& rhs ) { return add( lhs, rhs ); } private: std::string m_Data; }; std::string randomString( size_t n ) { std::string r; while( n-- ) { r += "0123456789"[rand()%10]; } return r; } int main() { srand( time(nullptr) ); for( int i = 0; i < 100; ++i ) { BigInteger lhs = randomString( 22 ); BigInteger rhs = randomString( 22 ); std::cout << lhs << " + " << rhs << " = " << lhs + rhs << '\n'; } }

BigInteger addition