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748 - Exponentiation
Time limit: 3.000 seconds
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=97&page=show_problem&problem=689
http://poj.org/problem?id=1001
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 
.
Input
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.Output
The output will consist of one line for each line of input giving the exact value of R n . Leading zeros and insignificant trailing zeros should be suppressed in the output.Sample Input
95.123 12 0.4321 20 5.1234 15 6.7592 9 98.999 10 1.0100 12
Sample Output
548815620517731830194541.899025343415715973535967221869852721 .00000005148554641076956121994511276767154838481760200726351203835429763013462401 43992025569.928573701266488041146654993318703707511666295476720493953024 29448126.764121021618164430206909037173276672 90429072743629540498.107596019456651774561044010001 1.126825030131969720661201
Description
现在要你解决的问题是：对一个实数R( 0.0 < R < 99.999 )，要求写程序精确计算 R 的 n 次方(R n)，其中n 是整数并且 0 < n <= 25。
Input
Output
参考资料：正则表达式30分钟入门教程
完整代码：
/*UVa: 0.242s*/
/*POJ: 125ms,3340KB*/import java.util.*;
import java.math.*;
import java.io.*;public class Main {static Scanner cin = new Scanner(new BufferedInputStream(System.in));public static void main(String[] args) {while (cin.hasNext()) {BigDecimal R = cin.nextBigDecimal();int n = cin.nextInt();String str = R.pow(n).stripTrailingZeros().toPlainString();// 返回移除所有尾部零的，不带指数字段的此BigDecimal的字符串表示形式if (str.indexOf("0") < str.indexOf("."))str = str.replaceFirst("^0*", "");// ^匹配字符串的开始，*表示重复零次或更多次System.out.println(str);}}
}
Source
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