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| package cn.edu.xidian.sselab.hashtable; import java.util.HashMap; import java.util.Map; /** * * @author zhiyong wang * title: Fraction to Recurring Decimal * content: * Given two integers representing the numerator and denominator of a fraction, return the fraction in string format. * If the fractional part is repeating, enclose the repeating part in parentheses. * * For example, * * Given numerator = 1, denominator = 2, return "0.5". * Given numerator = 2, denominator = 1, return "2". * Given numerator = 2, denominator = 3, return "0.(6)". * * */ public class FractiontoRecurringDecimal { //I cannot solve this problem by myself //这个题首先要考虑特殊情况（1）numerator是0的情况（2）denominator是0的情况（3）正负值问题 //然后因为返回的是字符串，而这个结果是拼凑的结果，所以要用StringBuilder的append方法来拼凑结果 //拼凑方式首先是取正负号(用异或的方式获取正负号)，(注意开始之前，两个数都要进行取绝对值操作)然后是整数部分，再然后是一个一个添加余数*10之后，除以分母的结果 //此时用HashMap来保存余数，与结果的长度，余数用来判断什么时候开始出现循环，长度用来记录添加括号的起始位置 public String fractionToDecimal(int numerator, int denominator){ if(numerator == 0) return "0"; if(denominator == 0) return null; StringBuilder strb = new StringBuilder(); // "+" or "-" strb.append(((numerator>0)^(denominator>0))?"-":""); long num = Math.abs((long)numerator); long den = Math.abs((long)denominator); // integral part strb.append(num/den); num %= den; if(num == 0) return strb.toString(); // fractional part strb.append("."); Map map = new HashMap(); while(num != 0){ if(!map.containsKey(num)){ map.put(num, strb.length()); num *= 10; strb.append(num/den); num %= den; }else{ int index = (int) map.get(num); strb.insert(index, "("); strb.append(")"); break; } } return strb.toString(); } } |
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原文地址：http://www.cnblogs.com/wzyxidian/p/5171410.html
