【HDU】1063 - Exponentiation（java - BigDecimal）

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Exponentiation

Time Limit: 2000/500 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 9008 Accepted Submission(s): 2611

Problem Description

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 R n where R is a real number ( 0.0 < R < 99.999 ) and n is an integer such that 0 < n <= 25.

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 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.

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

Source

East Central North America 1988

和那个阶乘的差不多，不过这个要注意去末尾的0，用 string 的 .stripTrailingZeros() 函数就行啦。

还有，再用一个 .toPlainString() 函数以免 ans 变为科学计数法。

输出的时候要注意是否是 0.xxx 这时候第一个零不能输出，那么就用 startsWith("0") 的方法查看第一位，然后用 .subString(1) 重新赋值。

代码如下：

import java.math.BigDecimal;
import java.util.Scanner;

public class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		while (sc.hasNext())
		{
			BigDecimal ans = sc.nextBigDecimal();
			int n = sc.nextInt();
			ans = ans.pow(n);
			String str = ans.stripTrailingZeros().toPlainString();
			if (str.startsWith("0"))
				str = str.substring(1);
			System.out.println(str);
		}
	}
}