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2013
11-09

POJ 1131 Octal Fractions [解题报告] Java

Octal Fractions

问题描述 :

Fractions in octal (base 8) notation can be expressed exactly in decimal notation. For example, 0.75 in octal is 0.953125 (7/8 + 5/64) in decimal. All octal numbers of n digits to the right of the octal point can be expressed in no more than 3n decimal digits to the right of the decimal point.

Write a program to convert octal numerals between 0 and 1, inclusive, into equivalent decimal numerals.

输入:

The input to your program will consist of octal numbers, one per line, to be converted. Each input number has the form 0.d1d2d3 … dk, where the di are octal digits (0..7). There is no limit on k.

输出:

Your output will consist of a sequence of lines of the form

0.d1d2d3 … dk [8] = 0.D1D2D3 … Dm [10]

where the left side is the input (in octal), and the right hand side the decimal (base 10) equivalent. There must be no trailing zeros, i.e. Dm is not equal to 0.

样例输入:

0.75
0.0001
0.01234567

样例输出:

0.75 [8] = 0.953125 [10]
0.0001 [8] = 0.000244140625 [10]
0.01234567 [8] = 0.020408093929290771484375 [10]

解题代码:

import java.io.*;
import java.util.*;
import java.math.*;
public class Main{
 public static void main(String[] args){
  Scanner cin=new Scanner(System.in);
  BigDecimal temp,sum,ans,num;
  String str;
  int i,len;
  while(cin.hasNext()){
   str=cin.next(); 
   len=str.length();
   temp=BigDecimal.valueOf(8.0);
   sum=BigDecimal.ONE;
   ans=BigDecimal.ZERO;
   for(i=2;i< len;i++)
   {
    int val=str.charAt(i)-'0';
    num=BigDecimal.valueOf(val);
    sum=sum.multiply(temp);
    ans=ans.add(num.divide(sum));
  }
  System.out.printf("%s [8] = ",str);
  System.out.println(ans+" [10]");
  }
 }
}

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