c++ - Unordered_map gets empty after inserting an element, what am I . . . I have an unordered_map object, which I fill somewhere, and when look for what I put, the map is empty When debugging, I can see that the size of classCMap is 1 at the end of the insertClassC() call, Unordered_map acts strange when I add a new element 0 C++ unordered_map weird behaviour Hot Network Questions
unordered_map - C++ Users Inserts new elements in the unordered_map Each element is inserted only if its key is not equivalent to the key of any other element already in the container (keys in an unordered_map are unique) This effectively increases the container size by the number of elements inserted The parameters determine how many elements are inserted and to which values they are initialized:
std::unordered_map lt;Key,T,Hash,KeyEqual,Allocator gt;:: insert_range unordered_map::size unordered_map::max_size unordered_map::empty Modifiers: unordered_map::clear Inserts a copy of each element in the range rg if and only if there is no element with key equivalent to the key of that element in * this the behavior is undefined: value_type is not EmplaceConstructible into unordered_map from
c++ - Why does unordered_map increase in size when it has enough . . . The cplusplus com website gives this explanation: void reserve (size_type n); Request a capacity change Sets the number of buckets in the container (bucket_count) to the most appropriate to contain at least n elements If n is greater than the current bucket_count multiplied by the max_load_factor, the container's bucket_count is increased and a rehash is forced
do value for keys are zero by default in unordered map in c++ - Reddit Precisely what u wonkey_monkey said Read the documentation for an unordered map, specifically operator[] If an element already exists with the specified key, a reference to that element will be returned But if an element with the specified key does not exist, a new element will be created and a reference to the new element returned
Demystifying std::unordered_map: A Key-Value Powerhouse in C++ Containers Compilation Errors Missing <unordered_map> Header Ensure you include the necessary header file: #include <unordered_map> ; Runtime Errors Modifying Keys Keys in std::unordered_map cannot be modified after insertion If you need to modify a key, you'll have to erase the existing key-value pair and insert a new one with the modified key