高精度运算类bign

Bign

1  #include<iostream>
  2  #include<string>
  3  #include<cstring>
  4  #include<cstdio>
  5  using namespace std;
  6  const int maxn = 1000 + 5;
  7  
  8  class bign
  9  {
 10  public:
 11      int len, s[maxn];
 12      bign()
 13      {
 14          len = 0;
 15          memset(s, 0, sizeof(s));
 16      }
 17      bign operator = (const char *num)
 18      {
 19          //支持对字符数组的赋值
 20          len = strlen(num);
 21          for(int i = 0; i < len; ++i)
 22              s[i] = num[len-i-1] - '0';
 23          return *this;
 24      }
 25      bign(const char *num)
 26      {
 27          //初始化
 28          *this = num;
 29      }
 30      bign operator = (int num)
 31      {
 32          //支持对整型数的赋值
 33          char s[maxn];
 34          sprintf(s, "%d", num);
 35          *this = s;
 36          return *this;
 37      }
 38      bign(int num)
 39      {
 40          //初始化
 41          *this = num;
 42      }
 43      string str() const
 44      {
 45          //x.str()不会改变x
 46          string str = "";
 47          for(int i = 0; i < len; ++i)
 48              str += (char)(s[i] + '0');//str = str + s[i] +'0'也可以
 49          if(str == "")
 50              str = "0";
 51          return str;
 52      }
 53      friend istream& operator>>(istream &in, bign& b);/*
 54      {
 55          string str;
 56          in >> str;
 57          b = str.c_str();
 58          return in;
 59      }*/
 60      friend ostream& operator<<(ostream &out, bign& b);/*
 61      {
 62          out << b.str();
 63          return out;
 64      }*/
 65      bign operator +(const bign& b) const
 66      {
 67          bign c;
 68          c.len = 0;
 69          /*
 70          int d = 0, i = 0;
 71          for(; d || i < max(len, b.len); ++i)
 72          {
 73          int x = d;
 74              if(i < len)
 75                  x += s[i];
 76              if(i < b.len)
 77                  x += b.s[i];
 78              c.s[c.len++] = x % 10;
 79              g = x % 10;
 80          }
 81          */
 82          // memset(c, 0, sizeof(c));
 83          int i = 0, d = 0;
 84          for(; i < max(len, b.len)+1; ++i)
 85          {
 86              int x = s[i] + b.s[i] + d;
 87              d = c.s[i] / 10;
 88              x %= 10;
 89              c.s[c.len++] = x;
 90          }
 91          if(d == 0)
 92              --c.len;
 93          return c;
 94      }
 95      bign operator +=(const bign& b)
 96      {
 97          *this = *this + b;
 98          return *this;
 99      }
100      bool operator <(const bign& b) const
101      {
102          if(len != b.len)
103              return len < b.len;
104          for(int i = len-1; i >= 0; --i)
105              if(s[i] != b.s[i])
106                  return s[i] < b.s[i];
107          return false;
108      }
109      bool operator >(const bign& b) const
110      {
111          return b < *this;
112      }
113      bool operator <= (const bign& b) const
114      {
115          return !(*this > b);
116      }
117      bool operator >=(const bign& b) const
118      {
119          return !(*this < b);
120      }
121      bool operator ==(const bign& b) const
122      {
123          return !(*this < b) && (*this > b);
124      }
125  };
126  
127  inline istream& operator>>(istream &in, bign& b)
128  {
129      string str;
130      in >> str;
131      b = str.c_str();
132      return in;
133  }
134  inline    ostream& operator<<(ostream &out, bign& b)
135  {
136      out << b.str();
137      return out;
138  }
139  int main()
140  {
141      return 0;
142  }

下面是一些实验：
Test

1 #include<iostream>
 2 #include<sstream>
 3 #include<cstring>
 4 #include<cstdio>
 5 using namespace std;
 6 
 7 int main()
 8 {
 9     __int64 n;
10     char a[1000];
11     while(cin >> n)
12     {
13         //注意整数不能溢出，cin返回错误直接退出
14         stringstream ss;
15         ss << n;
16         string str;
17         ss >> str;
18         cout << str;
19         cout << endl;
20         /*
21         //还是用C++的stringstream好，C的__int64依然是当做普通int操作的，容易出错
22         sprintf(a, "%d", n);
23         for(int i = 0; i < strlen(a); ++i)
24             cout << a[i];
25             */
26         cout << endl << "**********************String****************************" << endl;
27         string str = "";
28         //对string串字符方式的赋值
29         for(int i = 0; i < strlen(a); ++i)
30             str += (char)(a[i]);
31         if(str == "")
32             str = "0";
33         cout << str;
34         cout << endl << "**********************Input****************************" << endl;
35     }
36     return 0;
37 }

原文链接: https://www.cnblogs.com/sanghai/archive/2013/04/04/2999555.html

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