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Given a (decimal - e.g. 3.72) number that is passed in as a string, return the binary representation that is passed in as a string. If the fractional part of the number can not be represented accurately in binary with at most 32 characters, return ERROR.
For n = "3.72", return "ERROR".
For n = "3.5", return "11.1".
分析：
分成两个部分，整数部分用%和/，小数部分 *2 如果 <1 就为0，基数=基数；大于1,就为1,基数=基数-1
比如：
0.6*2=1.2>0 那么就为1 基数=1.2-1=0.2
0.2*2=0.4<0 那么就为0,基数=0.4
0.4*2=0.8<0,那么就为0,基数=0.8
0.8*2=1.6>0 那么就为1,基数为1.6-1=0.6
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所以5.6可以表示为:101.1001
1 public class Solution { 2 /** 3 *@param n: Given a decimal number that is passed in as a string 4 *@return: A string 5 */ 6 public String binaryRepresentation(String n) { 7 int intPart = Integer.parseInt(n.substring(0, n.indexOf(‘.‘))); 8 double decPart = Double.parseDouble(n.substring(n.indexOf(‘.‘))); 9 String intstr = ""; 10 String decstr = ""; 11 12 if (intPart == 0) intstr += ‘0‘; 13 while (intPart > 0) { 14 int c = intPart % 2; 15 intstr = c + intstr; 16 intPart = intPart / 2; 17 } 18 int count = 0; 19 while (decPart > 0.0 && count <= 32) { 20 double r = decPart * 2; 21 if (r >= 1.0) { 22 decstr += ‘1‘; 23 decPart = r - 1.0; 24 }else { 26 decstr += ‘0‘; 27 decPart = r; 28 } 29 count++; 30 } 31 32 if (count > 32) return "ERROR"; 33 return decstr.length() > 0? intstr + "." + decstr : intstr; 34 } 35 }
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原文地址：http://www.cnblogs.com/beiyeqingteng/p/5691435.html
