add: 220421-CN [cpp]

cpp/2204/220421.cpp

@@ -0,0 +1,75 @@
+struct Node {
+	int val;
+	Node* next;
+
+	explicit Node(int x, Node* n) : val(x), next(n) {}
+};
+
+/**
+ * 705. Design HashSet
+ * Design a HashSet without using any built-in hash table libraries.
+ * Implement MyHashSet class:
+ * void add(key) Inserts the value key into the HashSet.
+ * bool contains(key) Returns whether the value key exists in the HashSet or not.
+ * void remove(key) Removes the value key in the HashSet. If key does not exist in the HashSet, do nothing.
+ */
+
+class MyHashSetNormal {
+private:
+	static inline const int BUCKET_SIZE = 512;
+
+	Node* bucket[BUCKET_SIZE] = {};
+public:
+	MyHashSetNormal() = default;
+
+	void remove(int key) {
+		Node* ptr = this->bucket[key % BUCKET_SIZE];
+		if (ptr && ptr->val == key) {
+			this->bucket[key % BUCKET_SIZE] = ptr->next;
+			delete ptr;
+			return;
+		}
+		for (; ptr && ptr->next; ptr = ptr->next) {
+			if (ptr->next->val == key) {
+				auto* toDelete = ptr->next;
+				ptr->next = toDelete->next;
+				delete toDelete;
+			}
+		}
+	}
+
+	bool contains(int key) {
+		for (Node* ptr = this->bucket[key % BUCKET_SIZE]; ptr; ptr = ptr->next)
+			if (ptr->val == key)
+				return true;
+		return false;
+	}
+
+	void add(int key) {
+		if (this->contains(key))
+			return;
+		this->bucket[key % BUCKET_SIZE] = new Node(key, this->bucket[key % BUCKET_SIZE]);
+	}
+};
+
+#include <bitset>
+
+// Slower...
+class MyHashSet {
+private:
+	std::bitset<1000001> s;
+public:
+	MyHashSet() = default;
+
+	void remove(int key) {
+		s.reset(key);
+	}
+
+	bool contains(int key) {
+		return s.test(key);
+	}
+
+	void add(int key) {
+		s.set(key);
+	}
+};

cpp/2204/CMakeLists.txt

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