未完待续的C++大数类BigInteger
看着JAVA诱人的大数类在ACM中很好用，可是我不会JAVA，感觉为了大数类去学习JAVA太麻烦了，不如写个C++的大数类，目前还未完善，只有部分功能的雏形，因为现在知识有限，即使拿着C++ Primer Plus和刘汝佳的白书各种翻，也才写了这一点，不过目测除了前导零没有什么bug了，刚才拿这个代码A了个题。。然后我打算慢慢完善它。。。
1 #include <iostream> 2 #include <cstring> 3 using namespace std; 4 const int MAXLENTH = 10000; 5 class BigInteger 6 { 7 private: 8 char s[MAXLENTH+10]; 9 int len; 10 public: 11 void init(){memset(s, 0, sizeof(s)); len = 1;} 12 BigInteger(){init();} 13 friend istream& operator>> (istream &in, BigInteger &x); 14 friend ostream& operator<< (ostream &out, BigInteger &x); 15 BigInteger operator= (char *num); 16 BigInteger operator+ (BigInteger &y); 17 BigInteger operator+= (BigInteger &y); 18 }; 19 20 istream& operator>> (istream &in, BigInteger &x) 21 { 22 x.init(); 23 char str[MAXLENTH]; 24 in >> str; 25 x = str; 26 return in; 27 } 28 29 ostream& operator<< (ostream &out, BigInteger &x) 30 { 31 char ans[MAXLENTH]; 32 for(int i = 0; i < x.len; i++) 33 ans[i] = x.s[x.len-i-1] + '0'; 34 ans[x.len] = '\0'; 35 out << ans; 36 return out; 37 } 38 39 BigInteger BigInteger::operator= (char *num) 40 { 41 len = strlen(num); 42 for(int i = 0; i < len; i++) 43 s[i] = num[len-i-1] - '0'; 44 return *this; 45 } 46 47 BigInteger BigInteger::operator+ (BigInteger &y) 48 { 49 BigInteger z; 50 for(int i = 0, c = 0; i <= MAXLENTH; i++) 51 { 52 int sum = s[i] + y.s[i] + c; 53 z.s[i] = sum % 10; 54 c = sum / 10; 55 } 56 int j = MAXLENTH; 57 for( ; j > 0; j--) 58 if(z.s[j])break; 59 z.len = j+1; 60 return z; 61 } 62 63 BigInteger BigInteger::operator+= (BigInteger &y) 64 { 65 *this = *this + y; 66 return *this; 67 } 68 69 int main() 70 { 71 BigInteger a, b, c; 72 while(cin >> a >> b) 73 { 74 c = a + b; 75 cout << c << endl; 76 } 77 return 0; 78 }
