bignum 大数模板

  1 #include<cstdio> 
  2 #include<cstring>
  3 #include<string>
  4 #include<algorithm>
  5 #include<iostream>
  6 using namespace std;
  7 
  8 const int maxn = 2003;
  9 
 10 struct bign{
 11     int len, s[maxn];
 12     bign(){
 13         memset(s,0,sizeof(s));
 14         len= 1;
 15     }
 16     bign(int num)    {    *this = num;    }
 17     bign(const char *num)    {    *this = num;    }
 18     bign operator = (const int num){
 19         char s[maxn];
 20         sprintf(s,"%d",num);
 21         return *this = s;
 22     }
 23     bign operator = (const char *num){
 24         for(int i = 0; num[i] ==‘0‘; ++num) ;
 25         len = strlen(num);
 26         for(int i = 0; i < len; ++i)
 27             s[i] = num[len-1-i] -‘0‘;
 28         return *this;
 29     }
 30     bign operator + (const bign &b) const {
 31         bign c;
 32         c.len = 0;
 33         int maxlen = max(len, b.len);
 34         for(int i = 0, g = 0; g || i < maxlen; ++i){    // g是进位 
 35             int x = g;
 36             if(i < len)      x += s[i];
 37             if(i < b.len)    x += b.s[i];
 38             c.s[c.len++] = x % 10;
 39             g = x / 10;
 40         }
 41         return c;
 42     }
 43     bign operator += (const bign &b){
 44         return *this = *this + b;
 45     }
 46     void clean(){
 47         while(len >1 && !s[len-1])    --len;
 48     }
 49     bign operator * (const bign &b) const {
 50         bign c;
 51         c.len = len + b.len;
 52         
 53         for(int i = 0; i < len; ++i)
 54             for(int j = 0; j < b.len; ++j)
 55                 c.s[i+j] += s[i] * b.s[j];
 56                 
 57         for(int i = 0; i < c.len; ++i){
 58             c.s[i+1] += c.s[i]/10;
 59             c.s[i] %= 10;
 60         }
 61         c.clean();
 62         return c;
 63     }
 64     bign operator *= (const bign &b){
 65         return *this = *this * b;
 66     }
 67     bign operator -(const bign &b) const {
 68         bign c;
 69         c.len = 0;
 70         for(int i = 0, g = 0; i < len; ++i){    //此时的 g是退位
 71             int x = s[i]- g;
 72             if(i < b.len)    x -= b.s[i];
 73             if(x >= 0)    g = 0;
 74             else {
 75                 g = 1;
 76                 x += 10;
 77             }
 78             c.s[c.len++] = x;
 79         }
 80         c.clean();
 81         return c;
 82     }
 83     bign operator -= (const bign &b){
 84         return *this = *this - b;
 85     }
 86     bign operator / (const bign &b) const {
 87         bign c, f = 0;
 88         for(int i = len-1; i >= 0; --i){
 89             f *= 10;
 90             f.s[0] = s[i];
 91             while(f >= b){
 92                 f -= b;
 93                 ++c.s[i];
 94             }
 95         }
 96         c.len = len;
 97         c.clean();
 98         return c;
 99     }
100     bign operator /= (const bign &b){
101         return *this = *this / b;
102     }
103     bign operator % (const bign &b) const {
104         bign r = *this / b;
105         return *this- r*b;
106     }
107     bign operator %= (const bign &b){
108         return *this = *this % b;
109     }
110     bool operator < (const bign &b) const {
111         if(len != b.len)    return len < b.len;
112         for(int i= len-1; i>=0; --i)
113             if(s[i] != b.s[i])    return s[i] < b.s[i];
114         return 0;
115     }
116     bool operator > (const bign &b) const {
117         if(len != b.len)    return len > b.len;
118         for(int i = len-1; i >= 0; --i)
119             if(s[i] != b.s[i])    return s[i] > b.s[i];
120         return 0;
121     }
122     bool operator == (const bign &b) const {
123         return !(*this < b || *this > b);
124     }
125     bool operator != (const bign &b) const {
126         return !(*this == b);
127     }
128     bool operator <= (const bign &b) const {
129         return *this < b || *this == b;
130     }
131     bool operator >= (const bign &b) const {
132         return *this > b || *this == b;
133     }
134     string str() const {
135         string res = "";
136         for(int i = 0; i < len; ++i)
137             res = char(s[i]+‘0‘) + res;        //这里一定不能掉乱 +的顺序！ 
138         return res;
139     }
140 };
141 
142 istream& operator >> (istream &in, bign &x){
143     string s;
144     in >> s;
145     x = s.c_str();
146     return in;
147 }
148 
149 ostream& operator << (ostream &out, const bign &x){
150     out << x.str();
151     return out;
152 }
153 
154 int main()
155 {
156     bign a,b,c,d,e,f,g;
157     while(cin>>a>>b)
158     {
159         a.clean();
160         b.clean();
161         c = a+b;
162         d = a-b;
163         e = a*b;
164         f = a/b;
165         g = a%b;
166         cout<<"a+b = "<<c<<endl;
167         cout<<"a-b = "<<d<<endl;
168         cout<<"a*b = "<<e<<endl;
169         cout<<"a/b = "<<f<<endl;
170         cout<<"a%b = "<<g<<endl;
171         cout<<(a==b? "a = b":"a != b")<<endl;
172     }
173     return 0;
174 }