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

en/codes/cpp/chapter_hashing/hash_map_chaining.cpp

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+/**
+ * File: hash_map_chaining.cpp
+ * Created Time: 2023-06-13
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "./array_hash_map.cpp"
+
+/* Chained address hash table */
+class HashMapChaining {
+  private:
+    int size;                       // Number of key-value pairs
+    int capacity;                   // Hash table capacity
+    double loadThres;               // Load factor threshold for triggering expansion
+    int extendRatio;                // Expansion multiplier
+    vector<vector<Pair *>> buckets; // Bucket array
+
+  public:
+    /* Constructor */
+    HashMapChaining() : size(0), capacity(4), loadThres(2.0 / 3.0), extendRatio(2) {
+        buckets.resize(capacity);
+    }
+
+    /* Destructor */
+    ~HashMapChaining() {
+        for (auto &bucket : buckets) {
+            for (Pair *pair : bucket) {
+                // Free memory
+                delete pair;
+            }
+        }
+    }
+
+    /* Hash function */
+    int hashFunc(int key) {
+        return key % capacity;
+    }
+
+    /* Load factor */
+    double loadFactor() {
+        return (double)size / (double)capacity;
+    }
+
+    /* Query operation */
+    string get(int key) {
+        int index = hashFunc(key);
+        // Traverse the bucket, if the key is found, return the corresponding val
+        for (Pair *pair : buckets[index]) {
+            if (pair->key == key) {
+                return pair->val;
+            }
+        }
+        // If key not found, 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();
+        }
+        int index = hashFunc(key);
+        // Traverse the bucket, if the specified key is encountered, update the corresponding val and return
+        for (Pair *pair : buckets[index]) {
+            if (pair->key == key) {
+                pair->val = val;
+                return;
+            }
+        }
+        // If the key is not found, add the key-value pair to the end
+        buckets[index].push_back(new Pair(key, val));
+        size++;
+    }
+
+    /* Remove operation */
+    void remove(int key) {
+        int index = hashFunc(key);
+        auto &bucket = buckets[index];
+        // Traverse the bucket, remove the key-value pair from it
+        for (int i = 0; i < bucket.size(); i++) {
+            if (bucket[i]->key == key) {
+                Pair *tmp = bucket[i];
+                bucket.erase(bucket.begin() + i); // Remove key-value pair
+                delete tmp;                       // Free memory
+                size--;
+                return;
+            }
+        }
+    }
+
+    /* Extend hash table */
+    void extend() {
+        // Temporarily store the original hash table
+        vector<vector<Pair *>> bucketsTmp = buckets;
+        // Initialize the extended new hash table
+        capacity *= extendRatio;
+        buckets.clear();
+        buckets.resize(capacity);
+        size = 0;
+        // Move key-value pairs from the original hash table to the new hash table
+        for (auto &bucket : bucketsTmp) {
+            for (Pair *pair : bucket) {
+                put(pair->key, pair->val);
+                // Free memory
+                delete pair;
+            }
+        }
+    }
+
+    /* Print hash table */
+    void print() {
+        for (auto &bucket : buckets) {
+            cout << "[";
+            for (Pair *pair : bucket) {
+                cout << pair->key << " -> " << pair->val << ", ";
+            }
+            cout << "]\n";
+        }
+    }
+};
+
+/* Driver Code */
+int main() {
+    /* Initialize hash table */
+    HashMapChaining map = HashMapChaining();
+
+    /* Add operation */
+    // Add key-value pair (key, value) to the hash table
+    map.put(12836, "Ha");
+    map.put(15937, "Luo");
+    map.put(16750, "Suan");
+    map.put(13276, "Fa");
+    map.put(10583, "Ya");
+    cout << "\nAfter adding, the hash table is\nKey -> Value" << endl;
+    map.print();
+
+    /* Query operation */
+    // Enter key to the hash table, get value
+    string name = map.get(13276);
+    cout << "\nEnter student ID 13276, found name " << name << endl;
+
+    /* Remove operation */
+    // Remove key-value pair (key, value) from the hash table
+    map.remove(12836);
+    cout << "\nAfter removing 12836, the hash table is\nKey -> Value" << endl;
+    map.print();
+
+    return 0;
+}