C++高精度大整数模板

#include<stdio.h>#include<string.h>#include<math.h>#include<iostream>#include<algorithm>#include<string>using namespace std;struct Bigint {    // representations and structures    string a; // to store the digits    int sign; // sign = -1 for negative numbers, sign = 1 otherwise    // constructors    Bigint() {} // default constructor    Bigint( string b ) { (*this) = b; } // constructor for string        // some helpful methods    int size() { // returns number of digits        return (int)a.size();    }    Bigint inverseSign() { // changes the sign        sign *= -1;        return (*this);    }    Bigint normalize( int newSign ) { // removes leading 0, fixes sign        for( int i = (int)a.size() - 1; i > 0 && a[i] == '0'; i-- )            a.erase(a.begin() + i);        sign = ( a.size() == 1 && a[0] == '0' ) ? 1 : newSign;        return (*this);    }        // assignment operator    void operator = ( string b ) { // assigns a string to Bigint        a = b[0] == '-' ? b.substr(1) : b;        reverse( a.begin(), a.end() );        this->normalize( b[0] == '-' ? -1 : 1 );    }        // conditional operators    bool operator < ( const Bigint &b ) const { // less than operator        if( sign != b.sign ) return sign < b.sign;        if( a.size() != b.a.size() )            return sign == 1 ? a.size() < b.a.size() : a.size() > b.a.size();        for( int i = (int)a.size() - 1; i >= 0; i-- ) if( a[i] != b.a[i] )            return sign == 1 ? a[i] < b.a[i] : a[i] > b.a[i];        return false;    }    bool operator == ( const Bigint &b ) const { // operator for equality        return a == b.a && sign == b.sign;    }    // mathematical operators    Bigint operator + ( Bigint b ) { // addition operator overloading        if( sign != b.sign ) return (*this) - b.inverseSign();        Bigint c;        for(int i = 0, carry = 0; i<a.size() || i<b.size() || carry; i++ ) {            carry+=(i<a.size() ? a[i]-48 : 0)+(i<b.a.size() ? b.a[i]-48 : 0);            c.a += (carry % 10 + 48);            carry /= 10;        }        return c.normalize(sign);    }    Bigint operator - ( Bigint b ) { // subtraction operator overloading        if( sign != b.sign ) return (*this) + b.inverseSign();        int s = sign; sign = b.sign = 1;        if( (*this) < b ) return ((b - (*this)).inverseSign()).normalize(-s);        Bigint c;        for( int i = 0, borrow = 0; i < a.size(); i++ ) {            borrow = a[i] - borrow - (i < b.size() ? b.a[i] : 48);            c.a += borrow >= 0 ? borrow + 48 : borrow + 58;            borrow = borrow >= 0 ? 0 : 1;        }        return c.normalize(s);    }    Bigint operator * ( Bigint b ) { // multiplication operator overloading        Bigint c("0");        for( int i = 0, k = a[i] - 48; i < a.size(); i++, k = a[i] - 48 ) {            while(k--) c = c + b; // ith digit is k, so, we add k times            b.a.insert(b.a.begin(), '0'); // multiplied by 10        }        return c.normalize(sign * b.sign);    }    Bigint operator / ( Bigint b ) { // division operator overloading        if( b.size() == 1 && b.a[0] == '0' ) b.a[0] /= ( b.a[0] - 48 );        Bigint c("0"), d;        for( int j = 0; j < a.size(); j++ ) d.a += "0";        int dSign = sign * b.sign; b.sign = 1;        for( int i = (int)a.size() - 1; i >= 0; i-- ) {            c.a.insert( c.a.begin(), '0');            c = c + a.substr( i, 1 );            while( !( c < b ) ) c = c - b, d.a[i]++;        }        return d.normalize(dSign);    }    Bigint operator % ( Bigint b ) { // modulo operator overloading        if( b.size() == 1 && b.a[0] == '0' ) b.a[0] /= ( b.a[0] - 48 );        Bigint c("0");        b.sign = 1;        for( int i = (int)a.size() - 1; i >= 0; i-- ) {            c.a.insert( c.a.begin(), '0');            c = c + a.substr( i, 1 );            while( !( c < b ) ) c = c - b;        }        return c.normalize(sign);    }    // output method    void print() {        if( sign == -1 ) putchar('-');        for( int i = (int)a.size() - 1; i >= 0; i-- ) putchar(a[i]);        printf("\n");    }};

Bigint功能：

Bigint one=string("1");   常数赋值
Bigint zero=string("0");

string n;

Bigint nn=n; //赋值

==

+

-

*

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%
nn.print();   输出