The type Tree is already defined

同一个包中有相同名字的类

### C++ STL Map Usage and Examples In the context of C++, `std::map` is a part of the Standard Template Library (STL), which provides an associative container that stores elements formed by a combination of key-value pairs, where each unique key is associated with exactly one value. The keys within a map are always sorted following a specific criterion defined at compile time through template parameters. The declaration syntax for creating a map looks like this: ```cpp #include <map> // Declaration example using int as both KeyType and ValueType. std::map<int, int> myMap; ``` To insert or update entries into a map, use the subscript operator (`[]`) or member function `insert()`[^2]: ```cpp myMap[key] = value; // Using [] to add/update items directly. auto resultPair = myMap.insert(std::make_pair(key, value)); // Using insert(). if (!resultPair.second) { std::cout << "Insertion failed because the key already exists." << '\n'; } ``` For searching operations on maps, utilize the built-in method `find()`. This returns an iterator pointing either to the element whose key matches what was searched for or past-the-end when no match occurs. ```cpp auto it = myMap.find(searchKey); if(it != myMap.end()) { std::cout << "Found: " << (*it).second << "\n"; } else { std::cout << "Not found\n"; } ``` When working with custom types as keys inside a map, ensure these types support comparison operators since they rely upon them during insertion and lookup processes. Custom comparators can also be provided while declaring your map instance if default ones do not meet requirements[^1]. Additionally, understanding how underlying data structures work helps optimize performance further. For instance, knowing that internally most implementations employ some form of balanced binary search tree ensures logarithmic complexity O(log n) for common tasks such as adding new elements or looking up existing records[^3].
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