当用户在unordered_map中定制哈希函数时，无法解码g ++中的模糊编译器错误 [英] Cannot decode an obscured compiler error in g++ when user custom hash function in unordered_map
本文介绍了当用户在unordered_map中定制哈希函数时，无法解码g ++中的模糊编译器错误的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
这是我想要编译的代码：
#include< unordered_map>
#include< unordered_set>
#include< algorithm>
#include< iostream>
#include< sstream>
#include< vector>
#include< string>
using namespace std;
命名空间_LEET_MAX_POINTS_ON_A_LINE
{
struct Point
{
int x;
int y;
Point（）：x（0），y（0）{}
Point（int a，int b）：x（a），y（b）{}
}
struct SlantedLine
{
public：
int slope_numerator;
int slope_denominator;
int intercept_numerator;
int intercept_denominator;
};
struct SlantedLineHash
{
size_t operator（）（const SlantedLine& k）const
{
return k.slope_numerator ^ k.slope_denominator ^ k。 intercept_numerator ^ k.intercept_denominator;
}
};
struct SlantedLineEqual
{
size_t operator（）（const SlantedLine& line1，const SlantedLine& line2）const
{
return（line1.slope_numerator = = line2.slope_numerator）&& （line1.slope_denominator == line2.slope_denominator）&& （line1.intercept_numerator == line2.intercept_numerator）&& （line1.intercept_denominator == line2.intercept_denominator）;
}
};
类解决方案
{
public：
int maxPoints（vector< Point& points）
{
if （）== 0）
{
return 0;
}
unordered_map< SlantedLine，unordered_set< int>，SlantedLineHash，SlantedLineEqual> slantedLineToPointsMap;
unordered_map< int，unordered_set< int>> verticalLineToPointsMap;
for（size_t i = 0; i< points.size（）; i ++）
{
for（size_t j = i + 1; j< points.size（）; j ++ ）
{
int x1 = points [i] .x;
int y1 = points [i] .y;
int x2 = points [j] .x;
int y2 = points [j] .y;
if（x1 == x2）
{
unordered_map< int，unordered_set< int>> :: iterator probe = verticalLineToPointsMap.find（x1）;
if（probe == verticalLineToPointsMap.end（））
{
unordered_set< int>点数;
points.insert（i）;
points.insert（j）;
verticalLineToPointsMap.insert（pair< int，unordered_set< int>>（x1，points））;
}
else
{
probe-> second.insert（i）;
probe-> second.insert（j）;
}
}
else
{
int slope_numerator = y2 - y1;
int slope_denominator = x2 - x1;
int intercept_numerator = y1 * x2 - x1 * y2;
int intercept_denominator = x2 - x1;
simplify_fraction（& slope_numerator，& slope_denominator）;
simplify_fraction（& intercept_numerator，& intercept_denominator）;
倾斜线;
line.slope_numerator = slope_numerator;
line.slope_denominator = slope_denominator;
line.intercept_numerator = intercept_numerator;
line.intercept_denominator = intercept_denominator;
unordered_map< SlantedLine，unordered_set< int>，SlantedLine，SlantedLineEqual> :: iterator probe = slantedLineToPointsMap.find（line）;
if（probe == slantedLineToPointsMap.end（））
{
unordered_set< int>点数;
points.insert（i）;
points.insert（j）;
slantedLineToPointsMap.insert（pair< SlantedLine，unordered_set< int>>（line，points））;
}
else
{
probe-> second.insert（i）;
probe-> second.insert（j）;
}
}
}
}
size_t maxPoints = 0;
for（unordered_map< int，unordered_set< int>> :: iterator i = verticalLineToPointsMap.begin（）; i！= verticalLineToPointsMap.end（）; i ++）
{
maxPoints = max （maxPoints，i-> second.size（））;
}
for（unordered_map< SlantedLine，unordered_set< int>，SlantedLine，SlantedLineEqual> :: iterator i = slantedLineToPointsMap.begin（）; i！= slantedLineToPointsMap.end（）; i ++）
{
maxPoints = max（maxPoints，i-> second.size（））;
}
return maxPoints;
}
private：
void simplify_fraction（int * numerator，int * denominator）
{
int common_factor = gcd（* numerator，* denominator）
* numerator / = common_factor;
* denominator / = common_factor;
if（* denominator <0）
{
* numerator * = -1;
* denominator * = -1;
}
}
int gcd（int a，int b）
{
if（a< 0）
{
return gcd（-a，b）;
}
else if（b <0）
{
return gcd（a，-b）;
}
else if（b> a）
{
return gcd（b，a）;
}
else
{
if（b == 0）
{
return a;
}
else
{
return gcd（b，a％b）;
}
}
}
};
};
使用命名空间_LEET_MAX_POINTS_ON_A_LINE;
int LEET_MAX_POINTS_ON_A_LINE（）
{
解决方案;
return 0;
}
在Visual Studio 2015上编译得很好（有一些不相关的警告）但它在g ++上惨败（如在ideone上： https://ideone.com/d1Rs1I ）
这里是编译器输出：
在/ usr / include /来自/ usr / include / c ++ / 5 / unordered_map：47的$ c / 5 / bits / hashtable.h：35：0，
，来自prog.cpp的
：1：
/ usr /包括/ C ++ / 5 /位/ hashtable_policy.h：在实例化结构的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>'：
/ usr / include目录/ C ++ / 5 / type_traits：137：12：从要求结构的std :: __ and_<的std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> >'
/ usr / include / c ++ / 5 / type_traits：148：38：需要从'struct std :: __ not_< std :: __ and_< std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine& __detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
/usr/include/c++/5/bits/unordered_map.h:100:66：required from'class std :: unordered_map< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，std :: unordered_set< int> _LEET_MAX_POINTS_ON_A_LINE： ：SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLineEqual>'
prog.cpp：96：102：此处需要
/usr/include/c++/5/bits/hashtable_policy.h:85:34：错误：无匹配调用（常量_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine）（常量_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine&安培;）
noexcept（declval<常量_hash和放大器;>（）（declval<常量_key和放大器;>（）））>
^
在/usr/include/c++/5/bits/move.h:57:0包含的文件中，
来自/ usr / include / c ++ / 5 / bits / stl_pair。 h：59，
来自/ usr / include / c ++ / 5 / utility：70，
来自/ usr / include / c ++ / 5 / unordered_map：38，
来自prog.cpp：1 ：
/ usr / include目录/ C ++ / 5 / type_traits：在结构的std :: __ not_<实例;的std :: __ and_<的std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'：
/usr/include/c++/5/bits/unordered_map.h:100:66：从要求类的std :: unordered_map< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，性病:: unordered_set< INT>中_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLineEqual>'
prog.cpp：96：102：从这里需要
/ usr / include / c ++ / 5 / type_traits：148：38：error：'value'is不是'性病成员:: __ and_<的std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> >'
：public integral_constant< bool，！_Pp :: value>
^
在/ usr / include / c ++ / 5 / unordered_map：48：0，
从prog.cpp：1：
包含的文件/ usr / include / c ++ / 5 /位/ unordered_map.h：在类的std :: unordered_map< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，性病:: unordered_set< INT>中_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLineEqual>'的实例：
prog.cpp ：96：102：required from here
/usr/include/c++/5/bits/unordered_map.h:100:66：error：'value'不是'std :: __ not_< std :: __and_<的std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef __umap_hashtable< _Key，_Tp，_Hash，_Pred，_Alloc> _Hashtable;
^
/usr/include/c++/5/bits/unordered_map.h:107:45：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: key_type key_type;
^
/usr/include/c++/5/bits/unordered_map.h:108:47：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: value_type value_type;
^
/usr/include/c++/5/bits/unordered_map.h:109:48：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: mapped_type mapped_type;
^
/usr/include/c++/5/bits/unordered_map.h:110:43：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: hasher hasher;
^
/usr/include/c++/5/bits/unordered_map.h:111:46：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: key_equal key_equal;
^
/usr/include/c++/5/bits/unordered_map.h:112:51：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: allocator_type allocator_type;
^
/usr/include/c++/5/bits/unordered_map.h:117:45：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: pointer pointer;
^
/usr/include/c++/5/bits/unordered_map.h:118:50：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: const_pointer const_pointer;
^
/usr/include/c++/5/bits/unordered_map.h:119:47：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: reference reference;
^
/usr/include/c++/5/bits/unordered_map.h:120:52：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: const_reference const_reference;
^
/usr/include/c++/5/bits/unordered_map.h:121:46：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: iterator iterator;
^
/usr/include/c++/5/bits/unordered_map.h:122:51：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash <_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: const_iterator const_iterator;
^
/usr/include/c++/5/bits/unordered_map.h:123:51：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: local_iterator local_iterator;
^
/usr/include/c++/5/bits/unordered_map.h:124:57：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: const_local_iterator const_local_iterator;
^
/usr/include/c++/5/bits/unordered_map.h:125:47：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: size_type size_type;
^
/usr/include/c++/5/bits/unordered_map.h:126:52：error：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
typedef typename _Hashtable :: difference_type difference_type;
^
/usr/include/c++/5/bits/unordered_map.h:280:7：错误：'value'不是'std :: __ not_< std :: __ and_< std的成员:: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>，std :: __ detail :: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
operator =（initializer_list< value_type> __l）
^
/usr/include/c++/5/bits/unordered_map.h:379:2：error：'value'is不是'性病成员:: __ not_<的std :: __ and_<的std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
emplace（_Args& ... __args）
^
/usr/include/c++/5/bits/unordered_map.h:432:7：error：'value 不是的一员的std :: __ not_<的std :: __ and_<的std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
insert（const value_type& __x）
^
/usr/include/c++/5/bits/unordered_map.h:439:2：error：'value'不是的性病成员:: __ not_<的std :: __ and_<的std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
insert（_Pair&& __x）
^
/usr/include/c++/5/bits/unordered_map.h:499:7：错误：'value'不是的性病成员:: __ not_<的std :: __ and_<的std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
insert（initializer_list< value_type> __l）
^
/usr/include/c++/5/bits/unordered_map.h:645:7：错误：'value'不是的性病成员:: __ not_<的std :: __ and_<的std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
equal_range（const key_type& __x）
^
/usr/include/c++/5/bits/unordered_map.h:649:7：错误：'value'不是的性病成员:: __ not_<的std :: __ and_<的std :: __ is_fast_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine>中的std :: __细节:: __ is_noexcept_hash< _LEET_MAX_POINTS_ON_A_LINE :: SlantedLine，_LEET_MAX_POINTS_ON_A_LINE :: SlantedLine> > >'
equal_range（const key_type& __x）const
^
prog.cpp：在成员函数int _LEET_MAX_POINTS_ON_A_LINE :: Solution :: maxPoints（std :: vector< _LEET_MAX_POINTS_ON_A_LINE :: Point> ;&）'：
prog.cpp：97：29：error：'probe'未在此范围内声明
if（probe == slantedLineToPointsMap.end（））
^
prog.cpp：118：142：error：'i'未在此范围中声明
for（unordered_map< SlantedLine，unordered_set< int>，SlantedLine，SlantedLineEqual> :: iterator i = slantedLineToPointsMap.begin ）; i！= slantedLineToPointsMap.end（）; i ++）
^
编译器错误输出看起来非常相似在此主题张贴的那个。
创建一个带有std :: pair作为键的std :: unordered_map
肯定我的哈希函数是const。不确定为什么它仍然抱怨我的哈希函数不是const。
解决方案
您使用的是不正确的迭代器类型。 >
您有：
unordered_map< SlantedLine，unordered_set< int>，SlantedLineHash， SlantedLineEqual> slantedLineToPointsMap;
...
unordered_map< SlantedLine，unordered_set< int>，SlantedLine，SlantedLineEqual> :: iterator probe = slantedLineToPointsMap.find（line）
...
for（unordered_map< SlantedLine，unordered_set< int> SlantedLine，SlantedLineEqual> :: iterator i = slantedLineToPointsMap.begin（）; i！= slantedLineToPointsMap.end（）; i ++）
您可以看到您指定了一个错误的迭代器类型 - 将类型更改为 auto （这将帮助逃避这样的问题）或使用 unordered_map< SlantedLine，unordered_set< int>，SlantedLineHash，SlantedLineEqual> :: iterator p>
原始错误不是那么可怕 - 它告诉你，编译器需要 void SlantedLine :: operator（）（const SlantedLine&）const 。如果您将它添加到您的代码如下：
struct SlantedLine
{
public：
int slope_numerator;
int slope_denominator;
int intercept_numerator;
int intercept_denominator;
void operator（）（const SlantedLine&）const
{
}
};
它编译。它确实要求这个运算符，因为它认为 SlantedLine 是哈希类型。
Here is the code I am trying to compile:
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <vector>
#include <string>
using namespace std;
namespace _LEET_MAX_POINTS_ON_A_LINE
{
struct Point
{
int x;
int y;
Point() : x(0), y(0) {}
Point(int a, int b) : x(a), y(b) {}
};
struct SlantedLine
{
public:
int slope_numerator;
int slope_denominator;
int intercept_numerator;
int intercept_denominator;
};
struct SlantedLineHash
{
size_t operator()(const SlantedLine& k) const
{
return k.slope_numerator ^ k.slope_denominator ^ k.intercept_numerator ^ k.intercept_denominator;
}
};
struct SlantedLineEqual
{
size_t operator()(const SlantedLine& line1, const SlantedLine& line2) const
{
return (line1.slope_numerator == line2.slope_numerator) && (line1.slope_denominator == line2.slope_denominator) && (line1.intercept_numerator == line2.intercept_numerator) && (line1.intercept_denominator == line2.intercept_denominator);
}
};
class Solution
{
public:
int maxPoints(vector<Point>& points)
{
if (points.size() == 0)
{
return 0;
}
unordered_map<SlantedLine, unordered_set<int>, SlantedLineHash, SlantedLineEqual> slantedLineToPointsMap;
unordered_map<int, unordered_set<int>> verticalLineToPointsMap;
for (size_t i = 0; i < points.size(); i++)
{
for (size_t j = i + 1; j < points.size(); j++)
{
int x1 = points[i].x;
int y1 = points[i].y;
int x2 = points[j].x;
int y2 = points[j].y;
if (x1 == x2)
{
unordered_map<int, unordered_set<int>>::iterator probe = verticalLineToPointsMap.find(x1);
if (probe == verticalLineToPointsMap.end())
{
unordered_set<int> points;
points.insert(i);
points.insert(j);
verticalLineToPointsMap.insert(pair<int, unordered_set<int>>(x1, points));
}
else
{
probe->second.insert(i);
probe->second.insert(j);
}
}
else
{
int slope_numerator = y2 - y1;
int slope_denominator = x2 - x1;
int intercept_numerator = y1 * x2 - x1 * y2;
int intercept_denominator = x2 - x1;
simplify_fraction(&slope_numerator, &slope_denominator);
simplify_fraction(&intercept_numerator, &intercept_denominator);
SlantedLine line;
line.slope_numerator = slope_numerator;
line.slope_denominator = slope_denominator;
line.intercept_numerator = intercept_numerator;
line.intercept_denominator = intercept_denominator;
unordered_map<SlantedLine, unordered_set<int>, SlantedLine, SlantedLineEqual>::iterator probe = slantedLineToPointsMap.find(line);
if (probe == slantedLineToPointsMap.end())
{
unordered_set<int> points;
points.insert(i);
points.insert(j);
slantedLineToPointsMap.insert(pair<SlantedLine, unordered_set<int>>(line, points));
}
else
{
probe->second.insert(i);
probe->second.insert(j);
}
}
}
}
size_t maxPoints = 0;
for (unordered_map<int, unordered_set<int>>::iterator i = verticalLineToPointsMap.begin(); i != verticalLineToPointsMap.end(); i++)
{
maxPoints = max(maxPoints, i->second.size());
}
for (unordered_map<SlantedLine, unordered_set<int>, SlantedLine, SlantedLineEqual>::iterator i = slantedLineToPointsMap.begin(); i != slantedLineToPointsMap.end(); i++)
{
maxPoints = max(maxPoints, i->second.size());
}
return maxPoints;
}
private:
void simplify_fraction(int* numerator, int* denominator)
{
int common_factor = gcd(*numerator, *denominator);
*numerator /= common_factor;
*denominator /= common_factor;
if (*denominator < 0)
{
*numerator *= -1;
*denominator *= -1;
}
}
int gcd(int a, int b)
{
if (a < 0)
{
return gcd(-a, b);
}
else if (b < 0)
{
return gcd(a, -b);
}
else if (b > a)
{
return gcd(b, a);
}
else
{
if (b == 0)
{
return a;
}
else
{
return gcd(b, a % b);
}
}
}
};
};
using namespace _LEET_MAX_POINTS_ON_A_LINE;
int LEET_MAX_POINTS_ON_A_LINE()
{
Solution solution;
return 0;
}
The code compiled fine (with a unrelated few warnings) on Visual Studio 2015, but it failed miserably on g++ (as on ideone: https://ideone.com/d1Rs1I)
Here are the compiler output:
In file included from /usr/include/c++/5/bits/hashtable.h:35:0,
from /usr/include/c++/5/unordered_map:47,
from prog.cpp:1:
/usr/include/c++/5/bits/hashtable_policy.h: In instantiation of 'struct std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine>':
/usr/include/c++/5/type_traits:137:12: required from 'struct std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> >'
/usr/include/c++/5/type_traits:148:38: required from 'struct std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
/usr/include/c++/5/bits/unordered_map.h:100:66: required from 'class std::unordered_map<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, std::unordered_set<int>, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLineEqual>'
prog.cpp:96:102: required from here
/usr/include/c++/5/bits/hashtable_policy.h:85:34: error: no match for call to '(const _LEET_MAX_POINTS_ON_A_LINE::SlantedLine) (const _LEET_MAX_POINTS_ON_A_LINE::SlantedLine&)'
noexcept(declval<const _Hash&>()(declval<const _Key&>()))>
^
In file included from /usr/include/c++/5/bits/move.h:57:0,
from /usr/include/c++/5/bits/stl_pair.h:59,
from /usr/include/c++/5/utility:70,
from /usr/include/c++/5/unordered_map:38,
from prog.cpp:1:
/usr/include/c++/5/type_traits: In instantiation of 'struct std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >':
/usr/include/c++/5/bits/unordered_map.h:100:66: required from 'class std::unordered_map<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, std::unordered_set<int>, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLineEqual>'
prog.cpp:96:102: required from here
/usr/include/c++/5/type_traits:148:38: error: 'value' is not a member of 'std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> >'
: public integral_constant<bool, !_Pp::value>
^
In file included from /usr/include/c++/5/unordered_map:48:0,
from prog.cpp:1:
/usr/include/c++/5/bits/unordered_map.h: In instantiation of 'class std::unordered_map<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, std::unordered_set<int>, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLineEqual>':
prog.cpp:96:102: required from here
/usr/include/c++/5/bits/unordered_map.h:100:66: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef __umap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc> _Hashtable;
^
/usr/include/c++/5/bits/unordered_map.h:107:45: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::key_type key_type;
^
/usr/include/c++/5/bits/unordered_map.h:108:47: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::value_type value_type;
^
/usr/include/c++/5/bits/unordered_map.h:109:48: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::mapped_type mapped_type;
^
/usr/include/c++/5/bits/unordered_map.h:110:43: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::hasher hasher;
^
/usr/include/c++/5/bits/unordered_map.h:111:46: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::key_equal key_equal;
^
/usr/include/c++/5/bits/unordered_map.h:112:51: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::allocator_type allocator_type;
^
/usr/include/c++/5/bits/unordered_map.h:117:45: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::pointer pointer;
^
/usr/include/c++/5/bits/unordered_map.h:118:50: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::const_pointer const_pointer;
^
/usr/include/c++/5/bits/unordered_map.h:119:47: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::reference reference;
^
/usr/include/c++/5/bits/unordered_map.h:120:52: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::const_reference const_reference;
^
/usr/include/c++/5/bits/unordered_map.h:121:46: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::iterator iterator;
^
/usr/include/c++/5/bits/unordered_map.h:122:51: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::const_iterator const_iterator;
^
/usr/include/c++/5/bits/unordered_map.h:123:51: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::local_iterator local_iterator;
^
/usr/include/c++/5/bits/unordered_map.h:124:57: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::const_local_iterator const_local_iterator;
^
/usr/include/c++/5/bits/unordered_map.h:125:47: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::size_type size_type;
^
/usr/include/c++/5/bits/unordered_map.h:126:52: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
typedef typename _Hashtable::difference_type difference_type;
^
/usr/include/c++/5/bits/unordered_map.h:280:7: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
operator=(initializer_list<value_type> __l)
^
/usr/include/c++/5/bits/unordered_map.h:379:2: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
emplace(_Args&&... __args)
^
/usr/include/c++/5/bits/unordered_map.h:432:7: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
insert(const value_type& __x)
^
/usr/include/c++/5/bits/unordered_map.h:439:2: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
insert(_Pair&& __x)
^
/usr/include/c++/5/bits/unordered_map.h:499:7: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
insert(initializer_list<value_type> __l)
^
/usr/include/c++/5/bits/unordered_map.h:645:7: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
equal_range(const key_type& __x)
^
/usr/include/c++/5/bits/unordered_map.h:649:7: error: 'value' is not a member of 'std::__not_<std::__and_<std::__is_fast_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine>, std::__detail::__is_noexcept_hash<_LEET_MAX_POINTS_ON_A_LINE::SlantedLine, _LEET_MAX_POINTS_ON_A_LINE::SlantedLine> > >'
equal_range(const key_type& __x) const
^
prog.cpp: In member function 'int _LEET_MAX_POINTS_ON_A_LINE::Solution::maxPoints(std::vector<_LEET_MAX_POINTS_ON_A_LINE::Point>&)':
prog.cpp:97:29: error: 'probe' was not declared in this scope
if (probe == slantedLineToPointsMap.end())
^
prog.cpp:118:142: error: 'i' was not declared in this scope
for (unordered_map<SlantedLine, unordered_set<int>, SlantedLine, SlantedLineEqual>::iterator i = slantedLineToPointsMap.begin(); i != slantedLineToPointsMap.end(); i++)
^
The compiler error output does look very much alike the one posted on this thread.
Creating an std::unordered_map with an std::pair as key
But I am sure my hash function is const. Not sure why it is still complaining my hash function is not const.
解决方案
You are using an incorrect iterator type.
You have:
unordered_map<SlantedLine, unordered_set<int>, SlantedLineHash, SlantedLineEqual> slantedLineToPointsMap;
...
unordered_map<SlantedLine, unordered_set<int>, SlantedLine, SlantedLineEqual>::iterator probe = slantedLineToPointsMap.find(line);
...
for (unordered_map<SlantedLine, unordered_set<int>, SlantedLine, SlantedLineEqual>::iterator i = slantedLineToPointsMap.begin(); i != slantedLineToPointsMap.end(); i++)
You can see that you have specified a wrong iterator type - either change the type to auto (which will help escape such issues) or use unordered_map<SlantedLine, unordered_set<int>, SlantedLineHash, SlantedLineEqual>::iterator.
The original error is not that terrible - what it tells you is that the compiler requires void SlantedLine::operator()(const SlantedLine&) const. If you add it to your code like this:
struct SlantedLine
{
public:
int slope_numerator;
int slope_denominator;
int intercept_numerator;
int intercept_denominator;
void operator()(const SlantedLine&) const
{
}
};
It compiles. And it did ask for this operator since it perceived SlantedLine to be the hash type.
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