Create: 0706-design-hashmap.cpp

cpp/0706-design-hashmap.cpp

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+/*
+ Design a HashMap without using any built-in hash table libraries.
+
+ Designing a hash table using the chaining method, where a vector holds a list of pairs representing the key-value mappings.
+
+ Time: O(n)
+ Space: O(n)
+*/
+
+class MyHashMap {
+public:
+ const int N = 10010;
+ vector<list<pair<int, int>>> h; 
+
+ /** Initialize your data structure here. */
+ MyHashMap() {
+ h = vector<list<pair<int, int>>>(N);
+ }
+
+ list<pair<int, int>>::iterator find(int key) {
+ int t = key % N;
+ for (auto it = h[t].begin(); it != h[t].end(); it ++ ) {
+ if (it->first == key)
+ return it;
+ }
+ return h[t].end();
+ }
+
+ /** value will always be non-negative. */
+ void put(int key, int value) {
+ auto t = key % N;
+ auto it = find(key);
+ if (it == h[t].end()) h[t].push_back({key, value});
+ else it->second = value;
+ }
+
+ /** Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key */
+ int get(int key) {
+ auto t = key % N;
+ auto it = find(key);
+ if (it != h[t].end()) return it->second;
+ return -1;
+ }
+
+ /** Removes the mapping of the specified value key if this map contains a mapping for the key */
+ void remove(int key) {
+ auto t = key % N;
+ auto it = find(key);
+ if (it != h[t].end()) h[t].erase(it);
+ }
+};
+
+/**
+ * Your MyHashMap object will be instantiated and called as such:
+ * MyHashMap* obj = new MyHashMap();
+ * obj->put(key,value);
+ * int param_2 = obj->get(key);
+ * obj->remove(key);
+ */