地图怎么了？

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);


}

This program meant to read number of lines then lines, and then output the number of times each word has been repeated in start of lines

for example with this input:

3
Spain Donna Elvira
England Jane Doe
Spain Donna Anna

I expect :

England 1
Spain 2

but I receive :

Spain 3

and I'm sure the the variable name is what it should be each time but something is wrong with the map.

my build log when I changed it to 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* are compared as pointers, not as strings. Use std::string instead.

And as P0W mentioned, scanf , printf , gets are C-style. Maps and iterators are C++-style. Don't mix them. Use std::cin , std::cout , std::getline for IO in C++.

Answer 2

If you map with a char* as a key, you're really mapping the with the address of the string, not the string itself as a key. Since your buffer is identically allocated on the stack every time, it will most likely end up at the same address and map to the same value, no matter the content.

Mapping from std::string, the C++ alternative to C strings, will instead automatically use the content of the string as a key.