hdu1002

简单大数，纠结了很久，PE若干次，最后不能留空行

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
 
const int MAXN = 9999;
const int DLEN = 4;
const int DIGIT = 500;
 
// 数字在该类中每四位逆序存放。
// 实现了加减乘除着四个最基本的运算。
// 乘法的时间复杂度为)O(n^2)
// 以后会把它改成更加快的傅立叶变换
class BigNum {
public:
       BigNum() : len(1) { memset(a, 0, sizeof(a)); }
       BigNum(int );
       BigNum(const char []);
       BigNum(const BigNum &);
       BigNum &operator=(const BigNum &);
       BigNum operator+(const BigNum &) const;
       BigNum operator-(const BigNum &) const;
       BigNum operator*(const BigNum &) const;
       BigNum operator/(const int) const;
       friend ostream & operator<<(ostream &os, const BigNum &n);
       friend istream & operator>>(istream &is, const BigNum &n);
private:
       int a[DIGIT];
       int len;
};
BigNum::BigNum(int n)
{
       len = 0;
       memset(a, 0, sizeof(a));
       while (n) {
              a[len++] = n % (1 + MAXN);
              n /= (1 + MAXN);
       }
       if (len == 0) len = 1;
}
BigNum::BigNum(const char s[])
{
       int j, m, n;
      
       len = 0;
       memset(a, 0, sizeof(a));
       for (n = strlen(s) - 1; n >= 0; n -= 4) {
              m = 0;
              if ((j = n - 3) < 0) j = 0;
              while (j <= n) m = m * 10 + s[j++] - '0';
              a[len++] = m;
       }
}
BigNum::BigNum(const BigNum &n)
{
       *this = n;
}
BigNum &BigNum::operator=(const BigNum &n)
{
       int i;
      
       len = n.len;
       memset(a, 0, sizeof(a));
       for (i = 0; i < len; i++) a[i] = n.a[i];
       return *this;
}
BigNum BigNum::operator+(const BigNum &n) const
{
       BigNum t;
       int i, blen;
      
       blen = len > n.len ? len : n.len;
       for (i = 0; i < blen; i++) {
              t.a[i] += a[i] + n.a[i];
              if (t.a[i] > MAXN) {
                     t.a[i + 1]++;
                     t.a[i] -= (MAXN + 1);
              }
       }
       if (t.a[blen] == 0) blen--;
       t.len = blen + 1;
       return t;
}
// a must bigger to b...
BigNum BigNum::operator-(const BigNum & n) const
{
       int     i, j, big;
       BigNum t, a(*this);
      
       big = n.len > a.len ? n.len : a.len;
       for(i = 0 ; i < big; i++){
              if(a.a[i] < n.a[i]){
                     j = i + 1;
                     while(a.a[j] == 0) j++;
                     a.a[j--]--;
                     while(j > i) a.a[j--] += MAXN;
                     t.a[i] = a.a[i] + MAXN + 1 - n.a[i];
              } else t.a[i] = a.a[i] - n.a[i];
       }
       a.len = big;
       while(t.a[a.len - 1] == 0 && a.len > 1) a.len--;
       t.len = a.len;
       return t;
}
BigNum BigNum::operator*(const BigNum &n) const
{
       BigNum t;
       int     i, j, blen;
      
       for (i = 0; i < len; i++) {
              for (j = 0; j < n.len; j++) {
                     t.a[i + j] += a[i] * n.a[j];
                     if (t.a[i + j] > MAXN) {
                            t.a[i + j + 1] += t.a[i + j] / (MAXN + 1);
                            t.a[i + j] %= (MAXN + 1);
                     }
              }
       }
       t.len = len + n.len;
       while (t.a[t.len - 1] == 0 && t.len > 1) t.len--;
       return t;
}
BigNum BigNum::operator/(const int n) const
{
       BigNum t;
       int     i, down;
      
       down = 0;
       for (i = len - 1; i >= 0; i--) {
              t.a[i] = (down * (MAXN + 1) + a[i]) / n;
              down = a[i] + down*(MAXN + 1) - t.a[i]*n;
       }
       t.len = len;
       while (t.a[t.len - 1] == 0 && t.len > 1) t.len--;
       return t;
}
ostream & operator<<(ostream &os, const BigNum &n)
{
       int i;
      
       os << n.a[n.len - 1];
       for(i = n.len - 2 ; i >= 0 ; i--){
              os.width(DLEN);
              os.fill('0');
              os << n.a[i];
       }
       return os;
}
istream & operator>>(istream &is, BigNum &n)
{
       char    s[DIGIT * 4 + 1];
      
       is >> s;
       BigNum t(s);
       n = t;
       return is;
}

int main()
{
    int N;
    cin>>N;
    for(int i = 1; i <= N; i++)
    {
        BigNum A;
        BigNum B;
        cin>>A>>B;
        cout<<"Case "<<i<<":"<<endl;
        cout<<A<<" + "<<B<<" = "<<A+B<<endl;
        if(i != N)
             cout<<endl;
        
    }
    return 0;
}