大数模板

我花了很长时间写的大数模板，过了很多题，但是我相信还是有BUG的，欢迎大家指出！
这套模板目前已经实现了大数开方，四则运算，大数比较等功能，后面还有其他功能，我会陆续更新。
大数模板

struct BigInteger {
    vector<int>s;  //12345--54321

    void DealZero() { //处理前导0 
        for(int i = s.size() - 1; i > 0; --i){
            if(s[i] == 0) s.pop_back();
            else break;
        }
    }

    BigInteger operator = (long long num) { // 赋值运算符
        s.clear();
        vector<int>tmp;
        do{
            s.push_back(num % 10);
            num /= 10;
        }while(num);
        return *this;
    }

    BigInteger operator = (const string& str) { // 赋值运算符
        s.clear();
        for(int i = str.size() - 1; i >= 0; --i) s.push_back(str[i] - '0');
        this->DealZero();
        return *this;
    }

    BigInteger operator + (const BigInteger& b) const {
        BigInteger c;
        c.s.clear();
        int len1 = s.size(),len2 = b.s.size(); 
        for(int i = 0,g = 0; g > 0 || i < len1 || i < len2; ++i) {
            int x = g;
            if(i < len1) x += s[i];
            if(i < len2) x += b.s[i];
            c.s.push_back(x % 10);
            g = x / 10;
        }
        return c;
   }

   //大数减小数 
   BigInteger operator - (const BigInteger& b) const {
        BigInteger c;
        c.s.clear();
        int len1 = s.size(),g = 0; i < len1 || i < len2; ++i) {
            int x = g;
            if(i < len1) x += s[i];
            g = 0;
            if(i < len2) x -= b.s[i];   
            if(x < 0) {
                g = -1; //借位 
                x += 10;
            } 
            c.s.push_back(x);
        }
        c.DealZero();
        return c;
   }

   BigInteger operator * (const BigInteger& b) const {
        BigInteger c,tmp;
        c.s.clear();
        int len1 = s.size(),len2 = b.s.size();
        for(int i = 0; i < len1; ++i) {
            tmp.s.clear();tmp;
            int num = i;
            while(num--) tmp.s.push_back(0);
            int g = 0;
            for(int j = 0; j < len2; ++j) {
                int x = s[i] * b.s[j] + g;
                tmp.s.push_back(x % 10);
                g = x / 10;
            }
            if(g > 0) tmp.s.push_back(g);
            c = c + tmp;    
        }
        c.DealZero();
        return c;
   }

   //单精度除法 
   BigInteger operator / (const int b) const { 
        BigInteger c,tmp;
        c.s.clear();
        int len = s.size();
        int div = 0;
        for(int i = len - 1; i >= 0; --i) {
            div = div * 10 + s[i];
            while(div < b && i > 0) {
                div = div * 10 + s[--i];
            }
            tmp.s.push_back(div / b);
            div %= b;
        }
        for(int i = tmp.s.size() - 1; i >= 0; --i) c.s.push_back(tmp.s[i]);
        c.DealZero();
        return c;
   } 

   bool operator < (const BigInteger& b) const {
        int len1 = s.size(),len2 = b.s.size();
        if(len1 != len2) return len1 < len2;
        for(int i = len1 - 1; i >= 0; --i) {
            if(s[i] != b.s[i]) return s[i] < b.s[i];    
        }
        return false; //相等 
   }

   bool operator <= (const BigInteger& b) const {
        return !(b < *this);
   }
   string ToStr() {
        string ans;
        ans.clear();
        for(int i = s.size()-1; i >= 0; --i) 
            ans.push_back(s[i] + '0');
        return ans;
   }

   //大数开方 
/**大数开方用法说明： 字符串必须从第二个位置开始输入,且s[0] = '0' scanf("%s",s+1); */ 
   BigInteger SQRT(char *s) {
        string p = "";
        s[0]='0';
        if(strlen(s)%2 == 1)
            work(p,2,s+1,0);
        else
            work(p,s,0);
        BigInteger c;
        c.s.clear();
        c = p;
        return c;
   }


//开方准备 
//------------------------------------
    int l;
    int work(string &p,int o,char *O,int I){
        char c,*D=O ;
        if(o>0)
        {
            for(l=0;D[l];D[l++]-=10)
            {
                D[l++]-=120;
                D[l]-=110;
                while(!work(p,0,O,l))
                    D[l]+=20;
                p += (char)((D[l]+1032)/20);

            }
        }
        else
        {
            c=o+(D[I]+82)%10-(I>l/2)*(D[I-l+I]+72)/10-9;
            D[I]+=I<0 ? 0 : !(o=work(p,c/10,I-1))*((c+999)%10-(D[I]+92)%10);
        }
        return o;
    }
//-----------------------------------------
};

ostream& operator << (ostream &out,const BigInteger& x) {
    for(int i = x.s.size() - 1; i >= 0; --i)
        out << x.s[i];
    return out;
}

istream& operator >> (istream &in,BigInteger& x) {
  string s;
  if(!(in >> s)) return in;
  x = s;
  return in;
}

我相信肯定是有BUG，大家如果发现了请一定指出！谢谢！