BigInteger operator / (const BigInteger& b) const { assert(b > 0); // 除数必须大于0 BigInteger c = *this; // 商:主要是让c.s和(*this).s的vector一样大 BigInteger m; // 余数:初始化为0 for (int i = s.size()-1; i >= 0; i--) { m = m*BASE + s[i]; c.s[i] = bsearch(b, m); m -= b*c.s[i]; } return c.clean(); }
BigInteger operator - (const BigInteger& b) const { assert(b <= *this); // 减数不能大于被减数 BigInteger c; c.s.clear(); for (int i = 0, g = 0; ; i++) { if (g == 0 && i >= s.size() && i >= b.s.size()) break; int x = s[i] + g; if (i < b.s.size()) x -= b.s[i]; if (x < 0) {g = -1; x += BASE;} else g = 0; c.s.push_back(x); } return c.clean(); }
BigInteger operator * (const BigInteger& b) const { int i, j; LL g; vector<LL> v(s.size()+b.s.size(), 0); BigInteger c; c.s.clear(); for(i=0;i<s.size();i++) for(j=0;j<b.s.size();j++) v[i+j]+=LL(s[i])*b.s[j]; for (i = 0, g = 0; ; i++) { if (g ==0 && i >= v.size()) break; LL x = v[i] + g; c.s.push_back(x % BASE); g = x / BASE; } return c.clean(); }