POJ 1001 Exponentiation 模拟小数幂

模拟小数幂

小数点位 pos

非零末位 e

长度 len

只有三种情况　

　　pos > len

　　pos < e

　　e < pos < len

 #include <iostream>
 #include <cstring>
 using namespace std;
 int a[], b[], c[];
 void Cal()
 {
     memset(c, , sizeof(c));
     for(int i = ; i < ; i++)
         for(int j = ; j < ; j++)
             c[i+j] += a[i] * b[j];
     for (int i = ; i < ; i++){
         c[i+] += c[i]/;
         c[i] %= ;
     }
     memset(a, , sizeof(a));
     for (int i = ; i <= ; i++)
         a[i] = c[i];
 }
 char s[];
 int pos, n, len;
 int main()
 {
     while(cin>>s>>n)
     {
         memset(a,,sizeof(a));
         memset(b,,sizeof(b));
         memset(c,,sizeof(c));
         int t = ;
         for (int i = ; i >= ; i--)
         {
             if(s[i]=='.') pos = i;
             else b[t++] = s[i] - '';
         }
         a[] = ;
         for(int i = ; i <= n; i++) Cal();
         len = ;
         while(!c[len] && len>=) len--;
         int e = ;//末尾
         while(!c[e] && e<= len) e++;
         pos =  - pos; pos *= n;//小数点
         if(pos > len)
         {
             cout<<".";
             for (int i = pos-; i >= e; i--) cout<<c[i];
             cout<<endl;
         }
         else if(pos <= e)//整数
         {
             for (int i = len; i >= pos; i--) cout<<c[i];
             cout<<endl;
         }
         else//普通
         {
             for (int i = len; i >= pos; i--) cout<<c[i];
             cout<<".";
             for (int i = pos-; i >= e; i--) cout<<c[i];
             cout<<endl;
         }
     }
 }