POJ-1001-Exponentiation（高精度大数）

转载于 2019-08-09 11:42:00 发布 · 110 阅读

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原文链接：http://www.cnblogs.com/Staceyacm/p/11326270.html

本文介绍了一种使用Java的BigDecimal类精确计算大数幂次的方法。通过读取输入的基数和指数，程序能够准确计算出结果，并适当地处理小数点后的零。示例代码展示了如何使用stripTrailingZeros()和toPlainString()等方法来优化输出。

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 ⁿwhere 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

Sample Output

548815620517731830194541.899025343415715973535967221869852721
.00000005148554641076956121994511276767154838481760200726351203835429763013462401
43992025569.928573701266488041146654993318703707511666295476720493953024
29448126.764121021618164430206909037173276672
90429072743629540498.107596019456651774561044010001
1.126825030131969720661201
代码：

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


public class Main {
    public static void main(String[] args) {
    Scanner s = new Scanner(System.in);
    while(s.hasNext()){
        BigDecimal b = s.nextBigDecimal();
        BigDecimal ans = BigDecimal.valueOf(1);
        int n = s.nextInt();
        while(n-- > 0)
            ans = ans.multiply(b);
        String string = ans.stripTrailingZeros().toPlainString().toString();
        if(string.startsWith("0."))
            string = string.substring(1);
        System.out.println(string);
    }
        s.close();
    }
}

知识点总结
1、stripTrailingZeros() ，返回类型为BigDecimal的小于此数的但除去尾部的0的数值。

2、toPlainString()，返回BigDecimal类型的String类型字符串。

3、startsWith()，确定此实例的开头是否与指定的字符串匹配。

4、substring()，返回一个新的字符串，它是此字符串的一个子字符串。该子字符串始于指定索引处的字符，一直到此字符串末尾。

转载于:https://www.cnblogs.com/Staceyacm/p/11326270.html