如何解决C ++-排序算法看不到用户定义类型的重载“ <”运算符
bool operator<(Fraction& first,Fraction& second)
问题在于您的重载operator<
仅接受非常量参数,但是算法试图将对a的常量引用Fraction
与容器中的元素进行比较。
由于operator<
不修改比较对象的内容,因此应通过const引用来获取它们:
bool operator<(Fraction const & first,Fraction const & second)
解决方法
好的,所以我有一个名为1的用户定义类型fraction
,它表示具有分子和分母的普通分数。这是代码:
class Fraction
{
private:
int numerator;
int denominator;
public:
Fraction(int numer,int denom)
:numerator(numer),denominator(denom){}
int get_denom(){return denominator;}
int get_numer(){return numerator;}
};
如您所见,它完全在头文件中实现。
因此,我要使用排序算法对分数向量进行排序。这是重载的“ <”运算符的代码(注意:它与Fraction类放在同一文件中,但在类的外部):
bool operator<(Fraction& first,Fraction& second)
{
if(first.get_denom() == second.get_denom())
{
return first.get_numer()<second.get_numer()?true:false;
}
int first_num=first.get_denom();
int second_num=second.get_denom();
int lcm=(first_num*second_num)/gcd(first_num,second_num);
int first_new_numerator=(lcm/first_num)*first.get_numer();
int second_new_numerator=(lcm/second_num)*second.get_numer();
return first_new_numerator<second_new_numerator?true:false;
}
它所做的是检查分母是否相等,然后测试分子的值。如果它们不相等,则使用最小公倍数和gcd均衡它们。
真正的问题开始于我想在main中使用排序算法(编译时错误),这是主要代码:
Fraction parse_fraction(string& input)
{
stringstream fraction_string(input);
int numer;
fraction_string>>numer;
char seperator;
fraction_string>>seperator;
int denom;
fraction_string>>denom;
return Fraction(numer,denom);
}
int main()
{
vector<Fraction> fractions;
string input;
while(cin>>input)
{
if(input=="|") break;
fractions.push_back(parse_fraction(input));
}
sort(fractions.begin(),fractions.end);
for(int i=0;i<fractions.size();i++)
{
cout<<fractions[i];
}
return 0;
}
我得到的错误是(注意:我已经适当地重载了“ <<”运算符的分数,但不想在这里造成混乱):
/usr/include/c++/4.6/bits/stl_algo.h||In function ‘_RandomAccessIterator std::__unguarded_partition(_RandomAccessIterator,_RandomAccessIterator,const _Tp&) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Fraction*,std::vector<Fraction> >,_Tp = Fraction]’:|
/usr/include/c++/4.6/bits/stl_algo.h:2253|70|instantiated from ‘_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator,_RandomAccessIterator) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Fraction*,std::vector<Fraction> >]’|
/usr/include/c++/4.6/bits/stl_algo.h:2284|54|instantiated from ‘void std::__introsort_loop(_RandomAccessIterator,_Size) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Fraction*,_Size = long int]’|
/usr/include/c++/4.6/bits/stl_algo.h:5330|4|instantiated from ‘void std::sort(_RAIter,_RAIter) [with _RAIter = __gnu_cxx::__normal_iterator<Fraction*,std::vector<Fraction> >]’|
/home/vanio/Desktop/workspace/C++/Ordner/main.cpp:35|43|instantiated from here|
/usr/include/c++/4.6/bits/stl_algo.h|2212|error: no match for ‘operator<’ in ‘__first.__gnu_cxx::__normal_iterator<_Iterator,_Container>::operator* [with _Iterator = Fraction*,_Container = std::vector<Fraction>,__gnu_cxx::__normal_iterator<_Iterator,_Container>::reference = Fraction&]() < __pivot’|
/usr/include/c++/4.6/bits/stl_algo.h|2212|note: candidates are:|
/usr/include/c++/4.6/bits/stl_pair.h|207|note: template<class _T1,class _T2> bool std::operator<(const std::pair<_T1,_T2>&,const std::pair<_T1,_T2>&)|
/usr/include/c++/4.6/bits/stl_iterator.h|291|note: template<class _Iterator> bool std::operator<(const std::reverse_iterator<_Iterator>&,const std::reverse_iterator<_Iterator>&)|
/usr/include/c++/4.6/bits/stl_iterator.h|341|note: template<class _IteratorL,class _IteratorR> bool std::operator<(const std::reverse_iterator<_IteratorL>&,const std::reverse_iterator<_IteratorR>&)|
/usr/include/c++/4.6/bits/basic_string.h|2510|note: template<class _CharT,class _Traits,class _Alloc> bool std::operator<(const std::basic_string<_CharT,_Traits,_Alloc>&,const std::basic_string<_CharT,_Alloc>&)|
/usr/include/c++/4.6/bits/basic_string.h|2522|note: template<class _CharT,const _CharT*)|
/usr/include/c++/4.6/bits/basic_string.h|2534|note: template<class _CharT,class _Alloc> bool std::operator<(const _CharT*,_Alloc>&)|
/usr/include/c++/4.6/bits/stl_vector.h|1290|note: template<class _Tp,class _Alloc> bool std::operator<(const std::vector<_Tp,const std::vector<_Tp,_Alloc>&)|
/home/vanio/Desktop/workspace/C++/Ordner/Fraction.h|39|note: bool operator<(Fraction&,Fraction&)|
/home/vanio/Desktop/workspace/C++/Ordner/Fraction.h|39|note: no known conversion for argument 2 from ‘const Fraction’ to ‘Fraction&’|
/usr/include/c++/4.6/bits/stl_algo.h|2215|error: no match for ‘operator<’ in ‘__pivot < __last.__gnu_cxx::__normal_iterator<_Iterator,_Container>::reference = Fraction&]()’|
/usr/include/c++/4.6/bits/stl_algo.h|2215|note: candidates are:|
/usr/include/c++/4.6/bits/stl_pair.h|207|note: template<class _T1,Fraction&)|
/home/vanio/Desktop/workspace/C++/Ordner/Fraction.h|39|note: no known conversion for argument 1 from ‘const Fraction’ to ‘Fraction&’|
||=== Build finished: 22 errors,0 warnings ===|
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。