CODEWITHSUNDEEP
c++dictionarystliteratorchar
Alf-SW
Alf-SW

Reputation: 1

How to map 2 char* arrays directly into std::map<std::string,std::string>

I have 2 char arrays like "const char *arr1[ArrSize] = {"Blah1", "Wibble1", "Shrug1"};". For putting them into a vector I found a nice quick solution:

void fillVecTest()
{
    const int ArrSize = 3;
    const char *arr1[ArrSize] = {"Blah1", "Wibble1", "Shrug1"};
    const char *arr2[ArrSize] = {"Blah2", "Wibble2", "Shrug2"};
    std::vector<std::string> vec1(arr1, arr1+ArrSize);
    std::vector<std::string> vec2(arr2, arr2+ArrSize);
    std::vector<std::string>::iterator l_It1Vec1;
    std::vector<std::string>::iterator l_It = vec1.end();
    l_It = find(vec1.begin(), vec1.end(), std::string("Blah1"));
    if(l_It != vec1.end())
    {
      size_t l_pos = l_It - vec1.begin();
      printf("found %s, pos=%u val: %s\n", l_It->c_str(),l_pos, vec2[l_pos].c_str());
    }
 }

Now I thought it should be also possible to put both directly into a map as arr1 is the key and arr2 is the value. I tried some ways but I didn't succeed.

void fillMapTest()
{
    const int ArrSize = 3;
    const char *arr1[ArrSize] = {"Blah1", "Wibble1", "Shrug1"};
    const char *arr2[ArrSize] = {"Blah2", "Wibble2", "Shrug2"};
    std::map<std::string,std::string> map1;//(pair(arr1,arr1), pair(arr1+ArrSize,arr2+ArrSize));
    std::map<std::string,std::string>::iterator l_It1Map1;
    //l_It1Map1 = find(map1.begin(), map1.end(), std::string("Blah1"));
    if(l_It1Map1 != map1.end())
    {
      printf("found key: %s, val: %s\n",l_It1Map1->first.c_str(), l_It1Map1->second.c_str());
    }

}


int _tmain(int /*argc*/, _TCHAR* /*argv[]*/)
{
  fillVecTest();
  fillMapTest();
  return 0;
}

I think that just the commented lines in function "fillMapTest" would need to be solved. Constuctor and find don't work like I want.

Please has any STL expert an idea?

Upvotes: 0

Views: 1230

Answers (3)

andre
andre

Reputation: 7249

std::map<std::string, std::string> m;

for(int i = 0; i < ArrSize; i++) {
    std::pair<std::string, std::string> p =
        std::make_pair(std::string(arr1[i]), std::string(arr2[i]));
    m.insert(p);
}

If you really want to use the map constructor you need an iterator of pairs and the only way(i know) is to use a std::vector<std::pair<std::string, std::string> >::iterator but this seems to be an unneeded extra step to get the same result.

#include <vector>
#include <map>
#include <string>

std::vector<std::pair<std::string, std::string> > values;

for(int i = 0; i < ArrSize; i++) {
    std::pair<std::string, std::string> p =
        std::make_pair(std::string(arr1[i]), std::string(arr2[i]));
    values.push_back(p);
}

std::map<std::string, std::string> m(values.begin(), values.end());

Upvotes: 3

tzwickl
tzwickl

Reputation: 1371

for(int i = 0; i < ArrSize; i++) {
    m.insert(pair<string, string>(arr1[i], arr2[i]));
}

Upvotes: 0

Kerrek SB
Kerrek SB

Reputation: 476980

The easiest way to write this:

std::map<std::string, std::string> m {
    { "key1", "value1" },
    { "key2", "value2" },
};

This requires your compiler to support initializer lists (a feature of C++11).

Upvotes: 5

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