UVa 748 Exponentiation

用正则表达式+Java大数真是太爽了，不信？你用C++写一遍试试。

先上代码：

import java.math.BigDecimal;
import java.util.*;
import java.util.regex.*;

public class Main748 {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		BigDecimal bd;
		int n;
		double num;
		while(scan.hasNext()) {
			bd = scan.nextBigDecimal();
			n = scan.nextInt();
			String str = bd.pow(n).toPlainString();
			Pattern p = Pattern.compile("^0\.\d+");
	        java.util.regex.Matcher m = p.matcher(str);
	        if(m.matches() == true) {
	        	str = str.substring(1);
	        }
	        int l;
	        for(l=str.length()-1; ; l--) {
	        	if(str.charAt(l) != '0')break;
	        }
	        str = str.substring(0, l+1);
			System.out.println(str);
		}
	}
}

 

题目描述如下：

 

  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  .

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 Rⁿ. 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