add: 220422 [cpp]

cpp/2204/220422.cpp

@@ -0,0 +1,84 @@
+#include <unordered_map>
+
+struct Node {
+	int key, val;
+	Node* next;
+
+	explicit Node(int k, int v, Node* n) : key(k), val(v), next(n) {}
+};
+
+/**
+ * 706. Design HashMap
+ * Design a HashMap without using any built-in hash table libraries.
+ * Implement the MyHashMap class:
+ * MyHashMap() initializes the object with an empty map.
+ * void put(int key, int value) inserts a (key, value) pair into the HashMap. If the key already exists in the map, update the corresponding value.
+ * int get(int key) returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
+ * void remove(key) removes the key and its corresponding value if the map contains the mapping for the key.
+ *
+ */
+
+class MyHashMap {
+private:
+	static inline const int BUCKET_SIZE = 512;
+
+	Node* bucket[BUCKET_SIZE] = {};
+
+	Node* getPointer(int key) {
+		for (Node* ptr = this->bucket[key % BUCKET_SIZE]; ptr; ptr = ptr->next)
+			if (ptr->key == key)
+				return ptr;
+		return nullptr;
+	}
+
+public:
+	MyHashMap() = default;
+
+	int get(int key) {
+		auto* ptr = getPointer(key);
+		return ptr ? ptr->val : -1;
+	}
+
+	void put(int key, int value) {
+		auto* ptr = this->getPointer(key);
+		if (ptr)
+			ptr->val = value;
+		else
+			this->bucket[key % BUCKET_SIZE] = new Node(key, value, this->bucket[key % BUCKET_SIZE]);
+	}
+
+	void remove(int key) {
+		Node* ptr = this->bucket[key % BUCKET_SIZE];
+		if (ptr && ptr->key == key) {
+			this->bucket[key % BUCKET_SIZE] = ptr->next;
+			delete ptr;
+			return;
+		}
+		for (; ptr && ptr->next; ptr = ptr->next) {
+			if (ptr->next->key == key) {
+				auto* toDelete = ptr->next;
+				ptr->next = toDelete->next;
+				delete toDelete;
+			}
+		}
+	}
+};
+
+class MyHashMapSTL {
+private:
+	std::unordered_map<int, int> m;
+public:
+	MyHashMapSTL() = default;
+
+	int get(int key) {
+		return m.count(key) ? m[key] : -1;
+	}
+
+	void put(int key, int value) {
+		m[key] = value;
+	}
+
+	void remove(int key) {
+		m.erase(key);
+	}
+};

cpp/2204/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2204)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2204 220421.cpp)
+ADD_EXECUTABLE(2204 220422.cpp)