Create: 0706-design-hashmap.cpp

Author: tonngw

cpp/0706-design-hashmap.cpp

@@ -0,0 +1,59 @@
+/*
+    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);
+ */