How do I convert values from a vector to a map in c++?

Question

I want to do something like this. Is there a stl algorithm that does this easily?

for each(auto aValue in aVector)
{
    aMap[aValue] = 1;
}

Answer 1

Maybe like this:

std::vector<T> v;   // populate this

std::map<T, int> m;

for (auto const & x : v) { m[x] = 1; }

Answer 2

You might std::transform the std::vector into a std::map

std::vector<std::string> v{"I", "want", "to", "do", "something", "like", "this"};
std::map<std::string, int> m;
std::transform(v.begin(), v.end(), std::inserter(m, m.end()),
               [](const std::string &s) { return std::make_pair(s, 1); });

This creates std::pairs from the vector's elements, which in turn are inserted into the map.

---

Or, as suggested by @BenFulton, zipping two vectors into a map

std::vector<std::string> k{"I", "want", "to", "do", "something", "like", "this"};
std::vector<int> v{1, 2, 3, 4, 5, 6, 7};
std::map<std::string, int> m;

auto zip = [](const std::string &s, int i) { return std::make_pair(s, i); };
std::transform(k.begin(), k.end(), v.begin(), std::inserter(m, m.end()), zip);

Answer 3

If you have a vector of pairs, where the first item in the pair will be the key for the map, and the second item will be the value associated with that key, you can just copy the data to the map with an insert iterator:

std::vector<std::pair<std::string, int> > values {   
    {"Jerry", 1},
    { "Jim", 2},
    { "Bill", 3} };

std::map<std::string, int> mapped_values;

std::copy(values.begin(), values.end(), 
          std::inserter(mapped_values, mapped_values.begin()));

or, you could initialize the map from the vector:

std::map<std::string, int> m2((values.begin()), values.end());