poj水题-1001 一个简单的大数乘幂算法实现

  1 #include <iostream>
  2 #include <vector>
  3 #include <string>
  4 #include <strstream>
  5 
  6 
  7 using namespace std;
  8 
  9 string Str_Char_Muti(const string & str,const char c)
 10 {
 11     int Len = str.length();
 12     int mutitemp=0,addtemp=0;
 13     int i;
 14     string aim =str;
 15     for(i = 0;i<Len;++i)
 16     {
 17         mutitemp = (c -‘0‘)*(str[i]-‘0‘)+addtemp;
 18         aim[i] =(char) (mutitemp%10 +‘0‘);
 19         addtemp = mutitemp /10;
 20     }
 21     if(addtemp != 0)
 22         aim = aim +(char) (addtemp+‘0‘);
 23     return aim;
 24 }
 25 string Str_Add(const string &str_1,const string &str_2)
 26 {
 27     if("0" ==str_1)
 28         return str_2;
 29     if("0"==str_2)
 30         return str_1;
 31     int Llen,Slen;
 32     string copy_1 = str_1;
 33     string copy_2 = str_2;
 34     if(str_2.length()>str_1.length())
 35     {
 36         Slen = str_1.length();
 37         Llen = str_2.length();
 38         for(int i=0;i<Llen-Slen;++i)
 39         {
 40             copy_1 +=‘0‘;
 41         }
 42     }
 43     else 
 44     {
 45 
 46         Slen = str_2.length();
 47         Llen = str_1.length();
 48         for(int i=0;i<Llen-Slen;++i)
 49         {
 50             copy_2 +=‘0‘;
 51         }
 52     }
 53 
 54     int addtemp=0,jin =0;
 55     string aim (Llen ,‘0‘);
 56     int i;
 57     for(i=0 ; i<Llen ; ++i)
 58         {
 59             addtemp =( (copy_1[i] -‘0‘)+(copy_2[i]-‘0‘) )+jin;
 60             jin = addtemp /10;
 61             aim[i] =(char)( addtemp % 10 + ‘0‘ );
 62         }
 63     if(jin != 0)
 64     aim += (char) ( jin+‘0‘ );
 65 
 66     return aim;
 67 
 68 }
 69 string Str_Muti(const string &str_1,const string& str_2)
 70 {
 71     string aim = "0";
 72     string temp = "0";
 73     if(str_1=="1")
 74         return str_2;
 75     if(str_2=="1")
 76         return str_1;
 77     int Len_1 = str_1.length();
 78     int Len_2 = str_2.length();
 79     aim = "0";
 80     for(int i=0;i<Len_2;++i)
 81     {
 82         temp = Str_Char_Muti(str_1,str_2[i]);
 83         for(int j=0;j<i;++j)
 84         {
 85                 temp = ‘0‘+ temp;
 86         }
 87 
 88         aim = Str_Add(aim,temp);
 89     }
 90     return aim;
 91 }
 92 string delete_0(const string &str ,int pos )
 93 {
 94     string aim;
 95     int i=0;
 96     if(pos<str.length())
 97     {
 98         while(str[i] == ‘0‘&&i<=pos)
 99             i++;
100         if(i<pos)
101         {
102             string head(str,i,pos-i);
103             string rear(str,pos,str.length()-pos);
104             string r ="";
105             for(int j=0;j<rear.length();++j)
106                 if(‘0‘!= rear[j]) 
107                 {
108                     r = rear;
109                     break;
110                 }
111             aim = head +‘.‘+r;
112 
113         }
114         else 
115         {
116             string a(str,pos,str.length()-1);
117             aim = a;
118         }
119     }
120     else 
121     {
122         aim = str;
123         int a = pos-str.length() ;
124         while(a--)   
125         {
126             aim = aim +‘0‘;            
127         }
128         aim = aim + ‘.‘;
129     }
130     return aim;
131 }
132 int main ()
133 {
134 
135     int n;
136     int pos;
137     string s;
138     string str_a;
139     string one ="1";
140     while(cin>>s>>n)
141     {
142         pos = 0;
143         str_a = "";
144         string sum ="1"; 
145         for(int i= 0;i<6;++i)
146             {
147                 if(‘.‘==s[i])
148                     pos = 5-i;
149                 else str_a = s[i] +str_a;
150             }
151 
152         vector <string> di;
153         pos = pos *n;
154         while(n!=0)
155         {
156             if(n%2==1)
157             {
158                 di.push_back(str_a);
159             }
160             else 
161             {
162                 di.push_back(one);
163             }
164             str_a = Str_Muti(str_a,str_a);
165             n = n/2;
166         }
167 
168         for(int i=0;i<di.size();++i)
169         {
170             sum = Str_Muti(sum,di[i]);
171         }
172 
173             str_a = delete_0(sum,pos);
174 
175         for(int i=str_a.length()-1;i>-1;--i)
176         {
177             cout<<str_a[i];
178         }
179             cout<<endl;
180     }
181     return 0;
182 }