How to iterate through a std::map and std:

问题:

How to iterate through a std::map<string,int> and std::vector<int> using single for loop ?

I have seen this questions but could not solve my problem.

I am trying like this

map<string,int> data;
data["Shravan"] = 1;
data["Mama"] = 2;
data["Sa1"] = 3;
data["Jhandu"] = 4;

vector<int> values = {1,2,3,4};

for(const auto& it1: data,it2 : values) {
    // Do something 
}

Edit : I can not go through one by one. Because i am using the key of std::map and value of std::vector in the same function. Which will be called inside for loop.

Both the container of same size.

回答1:

If you know there's both the same length, use something like:

auto vit = begin(value);
auto mit = begin(data);
for (; vit != end(value); ++mit, ++vit) {
    // Use mit and vit
}

回答2:

How about a do-while? Provided that your containers aren't empty.

auto iv = std::begin(value);
auto id = std::begin(data);

do {
    // Use those iterators
} while(++iv != std::end(value) && ++id != std::end(data))

Or use while if you'd like to handle empty containers too.

auto iv = std::begin(value);
auto id = std::begin(data);

while(iv != std::end(value) && id != std::end(data)) {
    // Use those iterators

    iv++; id++;
}

回答3:

Consider boost::zip_iterator discussed in this answer https://stackoverflow.com/a/8513803/2210478

回答4:

You can iterate over both the map and the vector and make sure to check the iterators against the end of the corresponding container.

auto map_iter = data.begin();
auto vec_iter = value.begin();
for (; map_iter != data.end() && vec_iter != value.end();
       ++map_iter, ++vec_iter) {
    // Use map_iter and vec_iter
}