在这个示例中,程序会输出“Key exists in the map with value: 10”,因为键“banana”存在于unordered_map中。如果你将keyToCheck更改为一个不存在的键,如“date”,程序将输出“Key does not exist in the map”。
相反，我更愿意使用std::unordered_map::find。因此，如果您确定第一个键存在，但第二个键不存在，您...
key,因此您可以简单地使用 unordered_map::find方法来检查它是否存在: void addEmployee(std::string_view newName, int newTime) { // first check if they name already exists, if it does then do nothing and return auto it = myDictionary.find(newName); if (it != myDictionary.end()) { std...
and performs a rehash if necessary. Returns a pointer to the4//existing element if it exists, otherwise nullptr.5//6//Note that this function does forward exceptions if key_eq() throws, and never7//
When accessing with [], if the key does not exist, the map will insert a new element with the default value. When accessing with at(), if the key does not exist, an exception will be thrown. Using find() allows you to check if the key exists without modifying the map. ...
(public member function) insert_or_assign (C++17) inserts an element or assigns to the current element if the key already exists (public member function) inserter creates astd::insert_iteratorof type inferred from the argument (function template)...
The single-element-with-hint member functions, (3) and (4), return an iterator that points to the position where the new element was inserted into the unordered_map or, if an element with an equivalent key already exists, to the existing element....
key(). The behavior is undefined if nh is not empty and get_allocator() != nh.get_allocator().8) If nh is an empty node handle, does nothing and returns the end iterator. Otherwise, inserts the element owned by nh into the container, if the container doesn't already contain an ...
The single-element-with-hint member functions, (3) and (4), return an iterator that points to the position where the new element was inserted into the unordered_map or, if an element with an equivalent key already exists, to the existing element....
The single-element-with-hint member functions, (3) and (4), return an iterator that points to the position where the new element was inserted into the unordered_map or, if an element with an equivalent key already exists, to the existing element....