通过从向量中获取键以及与映射中的键对应的值来创建映射

Question

我有一个地图和一个矢量，我想通过从矢量中获取与地图中的钥匙对应的值来创建地图。我该怎么办？

Answer 1

我猜是这样的：

#include <iostream>
#include <map> 
#include <vector>


int main()
{
    std::map<int,int> dummy; 

    dummy.insert(std::pair<int,int>(1, 40)); 
    dummy.insert(std::pair<int,int>(2, 30)); 
    dummy.insert(std::pair<int,int>(3, 60)); 
    dummy.insert(std::pair<int,int>(4, 20)); 
    dummy.insert(std::pair<int,int>(5, 50)); 

    std::vector<int>v{1,3,5};

    std::map<int,int>  final; // Final map

    for(auto&e:v)
        final[e]=dummy[e]; // Set key from vector, get value from dummy.

    for(auto it = final.cbegin(); it != final.cend(); ++it)
    {
        std::cout << it->first << " " << it->second << "\n";
    }

}

Answer 2

据我了解的问题，您想要这样的东西。我创建它作为最小的示例。希望我能正确理解您的问题：

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

int main()
{
    // init example vector
    std::vector<std::string> keys;
    keys.push_back("key_1");
    keys.push_back("key_2");

    // ini example map
    std::map<std::string, std::string> someMap;
    someMap.insert(std::pair<std::string, std::string>("key_1", "val_1"));
    someMap.insert(std::pair<std::string, std::string>("key_3", "val_3"));

    // create new empty map for the results
    std::map<std::string, std::string> resultMap;

    // iterate over the vector an check keys against the map
    for(uint64_t i = 0; i < keys.size(); i++)
    {
        std::map<std::string, std::string>::const_iterator it;
        it = someMap.find(keys.at(i));

        // if key of the vector exist within the map, add the key with the value to the result map
        if(it != someMap.end())
        {
            resultMap.insert(std::pair<std::string, std::string>(it->first, it->second));
        }
    }

    // after this, the resultMap contains only "key_1" with "val_1", 
    // so only entries of the vector with the corresponding value within the map
}