Add the initial EN translation for C++ code (#1346)

en/codes/cpp/chapter_hashing/hash_map_open_addressing.cpp

@@ -0,0 +1,171 @@
+/**
+ * File: hash_map_open_addressing.cpp
+ * Created Time: 2023-06-13
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "./array_hash_map.cpp"
+
+/* Open addressing hash table */
+class HashMapOpenAddressing {
+  private:
+    int size;                             // Number of key-value pairs
+    int capacity = 4;                     // Hash table capacity
+    const double loadThres = 2.0 / 3.0;     // Load factor threshold for triggering expansion
+    const int extendRatio = 2;            // Expansion multiplier
+    vector<Pair *> buckets;               // Bucket array
+    Pair *TOMBSTONE = new Pair(-1, "-1"); // Removal mark
+
+  public:
+    /* Constructor */
+    HashMapOpenAddressing() : size(0), buckets(capacity, nullptr) {
+    }
+
+    /* Destructor */
+    ~HashMapOpenAddressing() {
+        for (Pair *pair : buckets) {
+            if (pair != nullptr && pair != TOMBSTONE) {
+                delete pair;
+            }
+        }
+        delete TOMBSTONE;
+    }
+
+    /* Hash function */
+    int hashFunc(int key) {
+        return key % capacity;
+    }
+
+    /* Load factor */
+    double loadFactor() {
+        return (double)size / capacity;
+    }
+
+    /* Search for the bucket index corresponding to key */
+    int findBucket(int key) {
+        int index = hashFunc(key);
+        int firstTombstone = -1;
+        // Linear probing, break when encountering an empty bucket
+        while (buckets[index] != nullptr) {
+            // If the key is encountered, return the corresponding bucket index
+            if (buckets[index]->key == key) {
+                // If a removal mark was encountered earlier, move the key-value pair to that index
+                if (firstTombstone != -1) {
+                    buckets[firstTombstone] = buckets[index];
+                    buckets[index] = TOMBSTONE;
+                    return firstTombstone; // Return the moved bucket index
+                }
+                return index; // Return bucket index
+            }
+            // Record the first encountered removal mark
+            if (firstTombstone == -1 && buckets[index] == TOMBSTONE) {
+                firstTombstone = index;
+            }
+            // Calculate the bucket index, return to the head if exceeding the tail
+            index = (index + 1) % capacity;
+        }
+        // If the key does not exist, return the index of the insertion point
+        return firstTombstone == -1 ? index : firstTombstone;
+    }
+
+    /* Query operation */
+    string get(int key) {
+        // Search for the bucket index corresponding to key
+        int index = findBucket(key);
+        // If the key-value pair is found, return the corresponding val
+        if (buckets[index] != nullptr && buckets[index] != TOMBSTONE) {
+            return buckets[index]->val;
+        }
+        // If key-value pair does not exist, return an empty string
+        return "";
+    }
+
+    /* Add operation */
+    void put(int key, string val) {
+        // When the load factor exceeds the threshold, perform expansion
+        if (loadFactor() > loadThres) {
+            extend();
+        }
+        // Search for the bucket index corresponding to key
+        int index = findBucket(key);
+        // If the key-value pair is found, overwrite val and return
+        if (buckets[index] != nullptr && buckets[index] != TOMBSTONE) {
+            buckets[index]->val = val;
+            return;
+        }
+        // If the key-value pair does not exist, add the key-value pair
+        buckets[index] = new Pair(key, val);
+        size++;
+    }
+
+    /* Remove operation */
+    void remove(int key) {
+        // Search for the bucket index corresponding to key
+        int index = findBucket(key);
+        // If the key-value pair is found, cover it with a removal mark
+        if (buckets[index] != nullptr && buckets[index] != TOMBSTONE) {
+            delete buckets[index];
+            buckets[index] = TOMBSTONE;
+            size--;
+        }
+    }
+
+    /* Extend hash table */
+    void extend() {
+        // Temporarily store the original hash table
+        vector<Pair *> bucketsTmp = buckets;
+        // Initialize the extended new hash table
+        capacity *= extendRatio;
+        buckets = vector<Pair *>(capacity, nullptr);
+        size = 0;
+        // Move key-value pairs from the original hash table to the new hash table
+        for (Pair *pair : bucketsTmp) {
+            if (pair != nullptr && pair != TOMBSTONE) {
+                put(pair->key, pair->val);
+                delete pair;
+            }
+        }
+    }
+
+    /* Print hash table */
+    void print() {
+        for (Pair *pair : buckets) {
+            if (pair == nullptr) {
+                cout << "nullptr" << endl;
+            } else if (pair == TOMBSTONE) {
+                cout << "TOMBSTONE" << endl;
+            } else {
+                cout << pair->key << " -> " << pair->val << endl;
+            }
+        }
+    }
+};
+
+/* Driver Code */
+int main() {
+    // Initialize hash table
+    HashMapOpenAddressing hashmap;
+
+    // Add operation
+    // Add key-value pair (key, val) to the hash table
+    hashmap.put(12836, "Ha");
+    hashmap.put(15937, "Luo");
+    hashmap.put(16750, "Suan");
+    hashmap.put(13276, "Fa");
+    hashmap.put(10583, "Ya");
+    cout << "\nAfter adding, the hash table is\nKey -> Value" << endl;
+    hashmap.print();
+
+    // Query operation
+    // Enter key to the hash table, get value val
+    string name = hashmap.get(13276);
+    cout << "\nEnter student ID 13276, found name " << name << endl;
+
+    // Remove operation
+    // Remove key-value pair (key, val) from the hash table
+    hashmap.remove(16750);
+    cout << "\nAfter removing 16750, the hash table is\nKey -> Value" << endl;
+    hashmap.print();
+
+    return 0;
+}