小白书73页bign类

const int maxn=1000;
struct bign
{
int len,s[MAXN];
bign(){
memset(s,0,sizeof(s));len=1;
}
bign opetator=(const char* num)
{
len=strlen(num);
for(int i=0;i<len;i++)
s[i]=num[len-i-i]-'0';
return *this;
}
bign operator=(int num)
{
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;
}
bign operator+=(const bign& b)
{
*this=*this+b;
return *this;
}
bool operator <(const bign& b) const
{
if(len!=b.len) return len<b.len;
for(int i=len-1;i>=0;i--)
if(s[i]!=b.s[i])  return s[i]<b.s[i];
return false;
}
bool operator>(const bign& b) const 
{
return b<*this;
}
bool operator<=(const bign& b) cosnt
{
return !(b<*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;
}