利用位乘，然后叠加

package coker;

import java.util.Scanner;

/**
 * Created by TaoHaoWei on 2017/9/23.
 * 本人新建博客：www.mynight.top
 * 欢迎交友和指正 ^_^
 * 滴滴，幂运算
 */
public class OutMi {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (true)
        {
            String  R = in.next();
            int n = in.nextInt();
            int flo = R.length()-R.indexOf(".")-1;
            R = R.replace(".","");
            StringBuilder sum = caculater(R.toCharArray(),n);
            flo *= n;
            flo = sum.length()-flo;
            sum.insert(flo,".");
            System.out.println(sum.toString());
        }

    }

    private static StringBuilder caculater(char[] r, int n) {
        int[] tmp = new int[r.length*2];
        StringBuilder sb = new StringBuilder();
        for (int i=0;i<r.length;i++)
            sb.append(r[i]);
        char[] zhu = r;
        while (n-->1)
        {
            int flag = tmp.length;

            int tt = 0;
            for (int i=zhu.length-1;i>=0;i--)
            {
                int t = 1;

                for(int j=r.length-1;j>=0;j--)
                {
                    tmp[flag-t-tt] += (r[j]-'0')*(zhu[i]-'0');
                    t++;
                }
                tt++;
            }
            for (int i=tmp.length-1;i>=0;i--)
            {
                if(tmp[i]>9)
                {
                    tmp[i-1] += tmp[i]/10;
                    tmp[i] %= 10;
                }
            }
            sb = new StringBuilder();
            int fir = 0;
            for (int i=0;i<tmp.length;i++)
            {
                if(fir==0&&tmp[i]==0)
                {

                }else{
                    fir++;
                    sb.append(tmp[i]);
                }
            }
            zhu = sb.toString().toCharArray();
            tmp = new int[zhu.length+r.length];
        }
        return sb;
    }
}