1、题目
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)".
wepon的解法
2.1 解析
2.2 代码
C++
/*
题目解析请参考博客：http://blog.csdn.net/u012162613/article/details/41998617
*/
class Solution {
public:
string fractionToDecimal(int numerator, int denominator) {
if(numerator==0) return "0";
string result;
if(numerator<0 ^ denominator<0 ) result+='-'; //异或，numerator<0和denominator<0仅有一个为真
//转化为正数，INT_MIN转化为正数会溢出，故用long long。long long int n=abs(INT_MIN)得到的n仍然是负的，所以写成下面的形式。
long long int n=numerator,d=denominator;
n=abs(n);d=abs(d);
result+=to_string(n/d); //整数部分
long long int r=n%d; //余数r
if(r==0) return result;
else result+='.';
//下面处理小数部分，用哈希表
unordered_map<int,int> map;
while(r){
//检查余数r是否在哈希表中，是的话则开始循环了
if(map.find(r)!=map.end()){
result.insert(map[r],1,'('); //http://www.cplusplus.com/reference/string/basic_string/insert/
result+=')';
break;
}
map[r]=result.size(); //这个余数对应于result的哪个位置
//正常运算
r*=10;
result+=to_string(r/d);
r=r%d;
}
return result;
}
};