大数问题

// 实数加减法
#include<cstdio>
#include<iostream>
#include<algorithm>
using namespace std;
string rever(string a)
{
        string b;
        for(int i = 0;i<a.size();i++)
        b = a[i] + b;
        return b;
}
int main()
{
   // freopen("input.txt","r",stdin);
    int n,m;
    string a,b;
    while(cin>>a>>b)
    {
        int i = 0,j = 0;
        while(a[i++]!='.'&&i<=a.size());
        if(i <= a.size())
        {
            n = a.size()-i;
            a.erase(a.begin()+i-1);
        }
        else n = 0;
      //  cout<<a<<" "<<b<<endl;
        while(b[j++]!='.'&&j<=b.size());
        if(j <= b.size())
        {
            m = b.size()-j;
            b.erase(b.begin()+j-1);
        }
        else m = 0;
        int mmax = max(n,m);
        while(n<m){
        a = a + '0';
        n++;
        }

        while(m<n){
        b = b + '0';
        m ++;
        }
        int g;
        a = rever(a);
        b = rever(b);
        char c[100008];
        int cn = 0;
        string s="";
       // puts("in");
        for(i=0,g=0;g||i<max(a.size(),b.size());i++)
        {
           int x = g;
           if(i<a.size())x+=a[i]-'0';
           if(i<b.size())x+=b[i]-'0';
           c[cn++] = x%10 +'0' ;
           s = c[cn-1] + s;

           g = x/10;
        }

        s.insert(s.end()-mmax,'.');
        for( i=s.size()-1;i>=0;i--)
        if(s[i]>'0'&&s[i]<='9')
        break;
        else{
        char cs = s[i];
        s.erase(s.begin()+i);
        if(cs == '.')break;
        }
        cout<<s<<endl;
    }
}

 
#include<string>
#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cstring>
using namespace std;
const int maxn = 1000;
struct  bign
{
    int len,s[maxn];
    bign()
    {
        memset(s,sizeof(s));
        len = 1;
    }

    bign operator = (const char *num)
    {
        len = strlen(num);
        for(int i=0;i<len;i++)s[i] = num[len-i-1] - '0';
        return *this;

    }
    bign operator = (int num)
    {
       // cout<<"in"<<endl;
        char s[maxn];
        sprintf(s,"%d",num);
        *this = s;
        return *this;
    }
    bign(int num){*this = num;}
    bign(const char *num){ *this = num ;}
    string str()const
    {
        string res = "";
        for(int i=0;i<len;i++)
        res = (char)(s[i] + '0') + res;
        if (res == "")res = "0";
        return res;
    }

    bign operator + (const bign& b)const
    {
       bign c;
       c.len = 0;
       for(int i=0,g = 0;g|| i<max(len,b.len);i++)
       {
           int x = g;
           if(i<len) x+= s[i];
           if(i<b.len) x+=b.s[i];
           c.s[c.len++] = x%10;
           g = x/10;
       }
       return c;

    }
     void clean()
    {
        while(len > 1 && !s[len-1]) len--;
    }

    bign operator += (const bign& b)
    {
        *this = *this + b;
        return *this;
    }
};
istream& operator >>(istream &in,bign& x)
{
    string s;
    in>>s;
    x = s.c_str();
    return in;
}
ostream& operator << (ostream &out,const bign& x)
{
   out << x.str();
    return out;
}
bign f[1002];
int main()
{
  for(int i=0;i<1000;i++)
  f[i] = 0;
  f[1] = 1;
  f[0] = 1;
  for(int i=2;i<=1000;i++)
  f[i] = f[i-1]+f[i-2];
  int m;
  while(cin>>f[1]>>f[2])
  {
      cout<<f[1]+f[2]<<endl;
  }

}
        

#include<stdio.h>
#include<cstring>
#include<iostream>
const int base = 10000;
const int Max = 100;
using namespace std;
void Mul(int a[],int fax,int b)
{
    int i,arr = 0;
    for(i = fax -1;i >= 0;i--)
    {
        arr +=b*a[i];
        a[i] = arr%base;
        arr /= base;
    }
}
void Div(int a[],div = 0;
    for(int i=0;i<fax;i++)
    {

        div = div*base + a[i];
        a[i] = div / b;
        div %= b;

    }
}
int main()
{
    int n,m,i;
    int a[101][Max];
    memset(a[1],Max*sizeof(int));
    for( i=2,a[1][Max-1] =1;i<101;i++)
    {
        memcpy(a[i],a[i-1],Max*sizeof(int));
        Mul(a[i],Max,4*i-2);
        Div(a[i],i+1);
    }
    while(cin>>n)
    {
        for( i=0;i<100&&a[n][i]==0;i++);
        cout<<a[n][i++];
        for(;i<Max;i++)
        {
            printf("%04d",a[n][i]);
        }
        cout<<endl;
    }
 return 0;
}