大数加法

#include<cstdio>

#include<cstring>

#include<vector>

#include<iostream>

#include <sstream>

#include <fstream>

using namespace std;

struct BigInteger {

static const int BASE = 100000000;

static const int WIDTH = 8;

vector<int> s;

BigInteger(long long num = 0) { *this = num; } // 构造函数

BigInteger(const string& str){*this=str;}

BigInteger operator = (long long num) { // 赋值运算符

this->s.clear();

do {

this->s.push_back(num % BASE);

num /= BASE;

} while(num > 0);

return *this;

}

BigInteger operator = (string const& str) { // 赋值运算符

s.clear();

int x, len = (str.length() - 1) / WIDTH + 1;

for(int i = 0; i < len; i++) {

int end = str.length() - i*WIDTH;

int start = max(0, end - WIDTH);

sscanf(str.substr(start,
4000
end-start).c_str(), "%d", &x);

s.push_back(x);

}

return *this;

}

BigInteger operator + (const BigInteger& b) const {

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 = g;

if(i < s.size()) x += s[i];

if(i < b.s.size()) x += b.s[i];

c.s.push_back(x % BASE);

g = x / BASE;

}

return c;

}

BigInteger operator +=(const BigInteger x)

{

*this=*this+x;

return x;

}

//该大整数类只有正数。

bool operator >(const BigInteger& b) const{

if(this->s.size()>b.s.size())

return 1;

else if(this->s.size()==b.s.size())

{

int size=s.size();

for(int i=size-1;i>=0;i--)

{

if(s[i]>b.s[i])

       return 1;

else

return 0;

}

return 0;

}

else

return 0;

}

//只做正数大减小的减法

BigInteger operator -(const BigInteger& b) const

{

  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 = g*BASE;

int x=0;

if(i < s.size()&&g==0) x += s[i];

else if(i<s.size()&&g==1) x+=s[i]-1;

if(i < b.s.size()) x -= b.s[i];

g=0;

if(x<0)

{

g=1;

x+=g*BASE;

}

c.s.push_back(x);

}

if(c.s.back()==0)

c.s.pop_back();

  return c;

}

};

ostream& operator << (ostream &out, const BigInteger&
e9ca
x) {

out << x.s.back();

for(int i = x.s.size()-2; i >= 0; i--) {

char buf[20];

sprintf(buf, "%08d", x.s[i]);

for(int j = 0; j < strlen(buf); j++) out << buf[j];

}

return out;

}

istream& operator >> (istream &in, BigInteger& x) {

string s;

if(!(in >> s)) return in;

x = s;

return in;

}

#include<set>

#include<map>

set<BigInteger> s;

map<BigInteger, int> m;

int main() {

string A,B;

cin>>A;

cin>>B;

if(A[0]!='-'&&B[0]!='-')

cout<<BigInteger(A)+BigInteger(B);

else if(A[0]=='-'&&B[0]=='-')

{

string a,b;

for(int i=1;i<A.length();i++)

{

a.push_back(A[i]);

}

for(int i=1;i<B.length();i++)

{

b.push_back(B[i]);

}

BigInteger sum;

sum=BigInteger(a)+BigInteger(b);

stringstream out;

string output;

out<<"-";

out << sum.s.back();

for(int i = sum.s.size()-2; i >= 0; i--) {

    char buf[20];

sprintf(buf, "%08d", sum.s[i]);

    for(int j = 0; j < strlen(buf); j++) out << buf[j];

}

out>>output;

cout<<output;

}

else if(A[0]!='-'&&B[0]=='-')

{

string a,b;

for(int i=0;i<A.length();i++)

{

a.push_back(A[i]);

}

for(int i=1;i<B.length();i++)

{

b.push_back(B[i]);

}

BigInteger At(a),Bt(b);

if(At>Bt)

cout<<At-Bt;

else

cout<<"-"<<Bt-At;

}

else

{

string temp=A; A=B; B=temp;

string a,b;

for(int i=0;i<A.length();i++)

{

a.push_back(A[i]);

}

for(int i=1;i<B.length();i++)

{

b.push_back(B[i]);

}

BigInteger At(a),Bt(b);

if(At>Bt)

cout<<At-Bt;

else

{

cout<<"-"<<Bt-At;

ofstream outfile;

outfile.open("123.txt");

outfile<<"-"<<Bt-At<<endl;

outfile.close();

}

}

return 0;