85 lines
1.9 KiB
C++
85 lines
1.9 KiB
C++
#include <unordered_map>
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struct Node {
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int key, val;
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Node* next;
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explicit Node(int k, int v, Node* n) : key(k), val(v), next(n) {}
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};
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/**
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* 706. Design HashMap
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* Design a HashMap without using any built-in hash table libraries.
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* Implement the MyHashMap class:
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* MyHashMap() initializes the object with an empty map.
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* 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.
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* 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.
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* void remove(key) removes the key and its corresponding value if the map contains the mapping for the key.
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*
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*/
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class MyHashMap {
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private:
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static inline const int BUCKET_SIZE = 512;
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Node* bucket[BUCKET_SIZE] = {};
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Node* getPointer(int key) {
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for (Node* ptr = this->bucket[key % BUCKET_SIZE]; ptr; ptr = ptr->next)
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if (ptr->key == key)
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return ptr;
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return nullptr;
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}
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public:
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MyHashMap() = default;
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int get(int key) {
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auto* ptr = getPointer(key);
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return ptr ? ptr->val : -1;
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}
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void put(int key, int value) {
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auto* ptr = this->getPointer(key);
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if (ptr)
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ptr->val = value;
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else
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this->bucket[key % BUCKET_SIZE] = new Node(key, value, this->bucket[key % BUCKET_SIZE]);
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}
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void remove(int key) {
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Node* ptr = this->bucket[key % BUCKET_SIZE];
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if (ptr && ptr->key == key) {
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this->bucket[key % BUCKET_SIZE] = ptr->next;
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delete ptr;
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return;
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}
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for (; ptr && ptr->next; ptr = ptr->next) {
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if (ptr->next->key == key) {
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auto* toDelete = ptr->next;
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ptr->next = toDelete->next;
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delete toDelete;
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}
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}
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}
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};
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class MyHashMapSTL {
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private:
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std::unordered_map<int, int> m;
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public:
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MyHashMapSTL() = default;
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int get(int key) {
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return m.count(key) ? m[key] : -1;
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}
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void put(int key, int value) {
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m[key] = value;
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}
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void remove(int key) {
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m.erase(key);
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}
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};
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