Problems involving the computation of exact values of very large magnitude and precision are common. For example, the computation of the national debt is a taxing experience for many computer systems.
This problem requires that you write a program to compute the exact value of Rn where R is a real number ( 0.0 < R < 99.999) and n is an integer such that $0 < n \le 25$.
The input will consist of a set of pairs of values for R and n. The R value will occupy columns 1 through 6, and the n value will be in columns 8 and 9.
The output will consist of one line for each line of input giving the exact value of Rn. Leading zeros and insignificant trailing zeros should be suppressed in the output.
95.123 12
0.4321 20
5.1234 15
6.7592 9
98.999 10
1.0100 12
548815620517731830194541.899025343415715973535967221869852721
.00000005148554641076956121994511276767154838481760200726351203835429763013462401
43992025569.928573701266488041146654993318703707511666295476720493953024
29448126.764121021618164430206909037173276672
90429072743629540498.107596019456651774561044010001
1.126825030131969720661201
#include<iostream>
#include<string.h>
using namespace std;
int main()
{
char str[1000],a[1000],a1[1000];
int c;
int n,i,j,k,t,x,num,t1,t2,y,y1,y2;
while(cin>>str>>n)
{
x=0;num=0;
t=strlen(str);
for(i=0;i<t;i++)
{
if(str[i]=='.')
{
num=t-1-i;
i++;
}
a[x]=str[i];
a1[x++]=str[i];
}
a[x]='\0';
a1[x]='\0';
num*=n;
int x1=x;
for(i=0;i<n-1;i++)
{
int sum[1000]={0};
t1=999;t2=999;
for(j=x-1;j>=0;j--)
{
for(k=x1-1;k>=0;k--)
sum[t1--]+=((a[j]-'0')*(a1[k]-'0'));
t2--;
t1=t2;
}
c=0;
for(y=999;y>=0;y--)
{
sum[y]+=c;
c=0;
if(sum[y]>9)
{
c=sum[y]/10;
sum[y]=sum[y]%10;
}
}
for(y1=0;y1<1000;y1++)
{
if(sum[y1]!=0)
break;
}
x1=0;
for(y2=y1;y2<1000;y2++)
a1[x1++]=sum[y2]+'0';
a1[x1]='\0';
}
if(num==0)
cout<<a1<<endl;
else
{
t=strlen(a1);
if(a1[t-1]=='0')//若(2.0, 2)则输出4而不是4.00，多余的零去掉
{
for(i=t-1;i>=0;i--)
{
if(a1[i]!='0')
break;
num--;//小数点的位数
}
t=i+1;
}
for(i=0;i<t-num;i++)
cout<<a1[i];//输出小数点之前的
cout<<".";
while(num>t-i)//若整数部分为0,小数部分不够填补小数点后的位数0
{
cout<<"0";
num--;
}
for(j=i;j<t;j++)
cout<<a1[j];//输出小数点后的
cout<<endl;
}
}
return 0;
}
原文：http://blog.csdn.net/phytn/article/details/41522611