POJ_1001 Exponentiation

 http://poj.org/problem?id=1001

/*
  Description:    基本思想很简单：把double型当做字符串进行读入，然后提取出double的各个数到int型
  数组中，模拟手算进行大整数乘法。
  注意：要事先计算出小数点的位置，输出的时候加以控制即可！
*/
#include<iostream>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<string>
#include<vector>

using namespace std;

typedef string::size_type size_type;

int ans[10024 + 10];

void Print(int *d, int size)
{
    for(int i = size - 1; i >= 0; --i)
      cout<<ans[i]<<" ";
    cout<<endl;
}

int Transfer(int *d, int size)
{
    int res = 0;
    memset(ans, 0, sizeof(ans));
   
    for(int i = 0; i < size; ++i){
      res = res*10 + d[i];
      ans[size-1-i] = d[i];
    }
    return res;
}

void Multiply(int& size, int r)
{
    int sh = 0;
    for(int i = 0; i < size; ++i){
       int temp = ans[i]*r + sh;
       ans[i] = temp%10;
       sh = temp/10;
    }
    int k = size;
    if(sh > 0){
       while(sh){
          ans[k++] = sh%10;
          sh /= 10;
       }
       size = k;
    }
}

int main()
{
   string dl;
   int n;
   while(cin>>dl>>n){
       size_type pos = dl.find('.', 0);
       int d[6] ;
       bool sign = 0;
       int index = 0;
       if(pos == string::npos)
          pos = dl.size();
         
          /*  begin-->提取出double*/
       for(size_type i = 0; i < pos; ++i)
          if(sign){
             d[index++] = dl[i] - '0';
          }
          else if(dl[i] != '0'){
             d[index++] = dl[i] - '0';
             sign = 1;
          }
       size_type up = dl.size() - 1;
       while(dl[up] == '0')
          --up;
       for(size_type i = pos+1; i <= up; ++i)
         d[index++] = dl[i] - '0';
         /*        end      */
      
       int r = Transfer(d, index);
      
       int size = index;
       for(int i = 1; i < n; ++i)
        Multiply(size, r);
       int point_pos = (up - pos)*n - 1;
      
       if(point_pos > size-1){
          cout<<".";
          for(int i = point_pos; i >= size; --i)
            cout<<0;
       }
      
       for(int i = size - 1; i >= 0; --i){
           if(i == point_pos)
             cout<<".";
           cout<<ans[i];
       }
       cout<<endl;
   }
   //system("pause");
   return 0;
}

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