这学期太忙了，一直没写什么东西（什么都没有学），等放假慢慢写点。今天刚好写到一个需要高精度的题，之前的高精度都是写了用完就扔，所以心血来潮打算直接完成一个高精度类，顺便练练运算符重载。
此类不限数字位数大小，支持cin与cout的单实例输入输出；支持加法与乘法以及+=和*=；支持所有逻辑比较运算；可以使用string，char数组或者long long及以下的整数初始化；=赋值和初始化等效，同样可以使用string、char和整数。
class BigInteger {
vector<int> bits;
public:
friend istream& operator >> (istream& BigIn, BigInteger& x) {
string num;
BigIn >> num;
x = num;
return BigIn;
}
friend ostream& operator << (ostream& BigOut, BigInteger x) {
for (auto it = x.bits.rbegin(); it != x.bits.rend(); ++it)
BigOut << *it;
return BigOut;
}
void operator=(const BigInteger& x)
{
this->bits.assign(x.bits.begin(), x.bits.end());
}
void operator=(string& s)
{
this->bits.clear();
for (auto it = s.rbegin(); it != s.rend(); ++it)
bits.emplace_back(*it - '0');
while (bits.size() && bits.back() == 0)
bits.pop_back();
}
void operator=(char* s)
{
this->bits.clear();
for (int i = strlen(s) - 1; i >= 0; --i)
bits.emplace_back(s[i] - '0');
while (bits.size() && bits.back() == 0)
bits.pop_back();
}
void operator=(long long x)
{
this->bits.clear();
while (x)
bits.emplace_back(x % 10), x /= 10;
while (bits.size()&&bits.back() == 0)
bits.pop_back();
}
bool operator>(const BigInteger& x)const
{
if (this->bits.size() != x.bits.size())
return this->bits.size() > x.bits.size();
else
{
for (int i = this->bits.size() - 1; i >= 0; --i)
if (this->bits[i] != x.bits[i])
return this->bits[i] > x.bits[i];
return 0;
}
}
bool operator==(const BigInteger& x)const
{
if (this->bits.size() != x.bits.size())
return 0;
else
{
for (int i = 0; i < x.bits.size(); ++i)
if (this->bits[i] != x.bits[i])
return 0;
return 1;
}
}
bool operator<(const BigInteger& x)const
{
if (this->bits.size() != x.bits.size())
return this->bits.size() < x.bits.size();
else
{
for (int i = this->bits.size() - 1; i >= 0; --i)
if (this->bits[i] != x.bits[i])
return this->bits[i] < x.bits[i];
return 0;
}
}
bool operator>=(const BigInteger& x)const
{
return *this > x || *this == x;
}
bool operator<=(const BigInteger& x)const
{
return *this < x || *this == x;
}
bool operator!=(const BigInteger& x)const
{
return !(*this == x);
}
BigInteger operator+(const BigInteger& x)const
{
BigInteger newNum(*this);
int minSize = min(this->bits.size(), x.bits.size());
for (int i = 0; i < minSize; ++i)
{
newNum.bits[i] += x.bits[i];
if (newNum.bits[i] >= 10 && i == newNum.bits.size() - 1)
newNum.bits.emplace_back(newNum.bits[i] / 10), newNum.bits[i] %= 10;
else if (newNum.bits[i] >= 10)
newNum.bits[i + 1] += newNum.bits[i] / 10, newNum.bits[i] %= 10;
}
return newNum;
}
void operator+=(const BigInteger& x) { *this = *this + x; }
BigInteger operator*(const BigInteger& x)const
{
BigInteger newNum;
newNum.bits.resize(this->bits.size() + x.bits.size(), 0);
for (int i = 0; i < this->bits.size(); ++i)
for (int j = 0; j < x.bits.size(); ++j)
{
int k = i + j;
if (k >= newNum.bits.size())
newNum.bits.emplace_back(this->bits[i] * x.bits[j]);
else
newNum.bits[k] += this->bits[i] * x.bits[j];
if (newNum.bits[k] >= 10 && k == newNum.bits.size() - 1)
newNum.bits.emplace_back(newNum.bits[k] / 10), newNum.bits[k] %= 10;
else if (newNum.bits[k] >= 10)
newNum.bits[k + 1] += newNum.bits[k] / 10, newNum.bits[k] %= 10;
}
while (newNum.bits.size()&&newNum.bits.back() == 0)
newNum.bits.pop_back();
return newNum;
}
void operator*=(const BigInteger& x) { *this = *this * x; }
int getBit(int i){return bits[i];}
int getLen() { return bits.size(); }
BigInteger() {}
BigInteger(const BigInteger& x)
{
this->bits.assign(x.bits.begin(), x.bits.end());
}
BigInteger(string s)
{
for (auto it = s.rbegin(); it != s.rend(); ++it)
bits.emplace_back(*it - '0');
while (bits.size() && bits.back() == 0)
bits.pop_back();
}
BigInteger(char* s)
{
for (int i = strlen(s) - 1; i >= 0; --i)
bits.emplace_back(s[i] - '0');
while (bits.size() && bits.back() == 0)
bits.pop_back();
}
BigInteger(long long x)
{
while (x)
bits.emplace_back(x % 10), x /= 10;
while (bits.size() && bits.back() == 0)
bits.pop_back();
}
BigInteger(BigInteger& x, int l = -1, int r = -1) {
if (l == -1 || r == -1)
l = 0, r = x.bits.size();
this->bits.clear();
for (int i = l; i < r; ++i)
this->bits.emplace_back(x.bits[i]);
}
};
//以下为使用示例
/*
int main()
{
ios::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
BigInteger x("12345679"), y(81);
char s[] = "0012345679";
x = s;
//cin >> x >> y;
cout << x << endl << y << endl << x + y << endl
<< x * y << endl << (x > y) << (x == y) << (x < y);
return 0;
}
*/
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