Question

#define _CRT_SECURE_NO_WARNINGS

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <map>
#include <iterator>
using namespace std;

int main()
{

    map<char*, int> m;
    int N;
    scanf ("%d", &N);

    for (int i = 0; i < N; i++)
    {
        char name[256], s[256];
        scanf ("%s", &name);
        gets (s);
        m[name]++;
    }
    map<char*, int>::iterator itr;
    for (itr = m.begin(); itr != m.end(); itr++)
        printf ("%s %d", itr->first, (itr)->second);


}

这个程序意味着读取行数然后行，然后输出每行在行开头重复的次数

例如使用此输入：

3
Spain Donna Elvira
England Jane Doe
Spain Donna Anna

我期待：

England 1
Spain 2

但我收到了：

Spain 3

我确定变量名称每次都应该是什么，但地图出了问题。

我将构建日志更改为std :: string

1>------ Build started: Project: UVa, Configuration: Debug Win32 ------
1>  UVa.cpp
1>c:\program files (x86)\microsoft visual studio 11.0\vc\include\xstddef(180): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xtree(2245) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xstddef(179) : while compiling class template member function 'bool std::less<_Ty>::operator ()(const _Ty &,const _Ty &) const'
1>          with
1>          [
1>              _Ty=std::string
1>          ]
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\map(194) : see reference to function template instantiation 'bool std::less<_Ty>::operator ()(const _Ty &,const _Ty &) const' being compiled
1>          with
1>          [
1>              _Ty=std::string
1>          ]
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\type_traits(743) : see reference to class template instantiation 'std::less<_Ty>' being compiled
1>          with
1>          [
1>              _Ty=std::string
1>          ]
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xtree(1028) : see reference to class template instantiation 'std::is_empty<_Ty>' being compiled
1>          with
1>          [
1>              _Ty=std::less<std::string>
1>          ]
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\map(67) : see reference to class template instantiation 'std::_Tree<_Traits>' being compiled
1>          with
1>          [
1>              _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false>
1>          ]
1>          c:\users\amiraz\documents\visual studio 2012\projects\uva\uva\uva.cpp(13) : see reference to class template instantiation 'std::map<_Kty,_Ty>' being compiled
1>          with
1>          [
1>              _Kty=std::string,
1>              _Ty=int
1>          ]
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xtree(2245) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xtree(2245) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xtree(2245) : see declaration of 'std::operator <'
1>c:\program files (x86)\microsoft visual studio 11.0\vc\include\xstddef(180): error C2784: 'bool std::operator <(const std::move_iterator<_RanIt> &,const std::move_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::move_iterator<_RanIt> &' from 'const std::string'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1983) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1983) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1983) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1983) : see declaration of 'std::operator <'
1>c:\program files (x86)\microsoft visual studio 11.0\vc\include\xstddef(180): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1259) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1259) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1259) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1259) : see declaration of 'std::operator <'
1>c:\program files (x86)\microsoft visual studio 11.0\vc\include\xstddef(180): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1075) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1075) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1075) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(1075) : see declaration of 'std::operator <'
1>c:\program files (x86)\microsoft visual studio 11.0\vc\include\xstddef(180): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\utility(232) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\utility(232) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\utility(232) : see declaration of 'std::operator <'
1>          c:\program files (x86)\microsoft visual studio 11.0\vc\include\utility(232) : see declaration of 'std::operator <'
1>c:\program files (x86)\microsoft visual studio 11.0\vc\include\xstddef(180): error C2676: binary '<' : 'const std::string' does not define this operator or a conversion to a type acceptable to the predefined operator
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Answer 1

char*被比较为指针，而不是字符串。请改用std::string。

正如P0W所述，scanf，printf，gets是C风格。映射和迭代器是C ++风格的。不要混合它们。在C ++中使用std::cin，std::cout，std::getline表示IO。

Answer 2

如果您使用char*作为键映射，那么您实际上是使用字符串的地址进行映射，而不是将字符串本身作为键映射。由于您的缓冲区每次都在堆栈上进行相同的分配，因此无论内容如何，它都很可能最终位于同一地址并映射到相同的值。

从std :: string（C字符串替代C字符串）映射，将自动使用字符串的 content 作为键。

地图有什么问题？

2 个答案: