2013
11-26

Exponentiation

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 <= 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 R^n. Leading zeros should be suppressed in the output. Insignificant trailing zeros must not be printed. Don’t print the decimal point if the result is an integer.

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

import java.io.*;
import java.util.*;
import java.math.*;
public class Main{
public static void main(String[] args){
Scanner cin = new Scanner(System.in);
while(cin.hasNextBigDecimal()){
BigDecimal num = cin.nextBigDecimal();
int n = cin.nextInt();
num = num.pow(n);
String r = num.stripTrailingZeros().toPlainString();
if(r.startsWith("0.")){
r = r.substring(1);
}
System.out.println(r);
}
}
}

java中高精度就是好用啊！以后得多学一下。虽然程序的效率差，但是写起代码简单。

num.pow(int n)方法的功能是计算一个数的幂；

num.stripTrailingZeros()方法的功能是返回不大于此数但是除去尾部0的数值。

num.toPlainString()方法的功能是转换为相应的字符串。

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2. 可以根据二叉排序树的定义进行严格的排序树创建和后序遍历操作。如果形成的排序树相同，其树的前、中、后序遍历是相同的，但在此处不能使用中序遍历，因为，中序遍历的结果就是排序的结果。经在九度测试，运行时间90ms，比楼主的要快。