( 大数 startsWith substring) Exponentiation hdu1063

Exponentiation

Time Limit: 2000/500 MS (Java/Others)????Memory Limit: 65536/32768 K (Java/Others)

Total Submission(s): 10319????Accepted Submission(s): 3027

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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.

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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.

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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.

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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.

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Sample Input

95.123 12 0.4321 20 5.1234 15 6.7592 9 98.999 10 1.0100 12

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Sample Output

548815620517731830194541.899025343415715973535967221869852721 .00000005148554641076956121994511276767154838481760200726351203835429763013462401 43992025569.928573701266488041146654993318703707511666295476720493953024 29448126.764121021618164430206909037173276672 90429072743629540498.107596019456651774561044010001 1.126825030131969720661201

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利用BigDecimal

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import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        BigDecimal a;
        while(in.hasNextBigDecimal()) {
            a=in.nextBigDecimal();
            int  b=in.nextInt();
            String s=a.pow(b).stripTrailingZeros().toPlainString();   //最后成了字符串。
            if(s.startsWith("0")) { s=s.substring(1); } //startsWith()是判断字符串是否以某个字符串开头，若是，返回true，String.substring(int start)参数：start：要截取位置的索引。返回：从start开始到结束的字符串。
            System.out.println(s);
        }
    }
}