Add Simple example: Hash Table

Author: icgw

DataStructure/Hash/example.cpp

@@ -0,0 +1,49 @@
+/*
+ * example.cpp
+ * Copyright (C) 2019 Guowei Chen <[email protected]>
+ *
+ * Distributed under terms of the MIT license.
+ */
+
+
+#include <iostream>
+#include <cstdlib>
+#include <ctime>
+#include "hash_table.hpp"
+
+constexpr int N         = 48;
+constexpr int MAX_VALUE = 1000;
+
+int main()
+{
+  srand(time(nullptr));
+
+  hash_table table;
+
+  // TEST: insert.
+  for (int i = 0; i < N; ++i) {
+    pRecord r = (pRecord) malloc(sizeof(Record));
+
+    r->key  = rand() % MAX_VALUE;
+    r->value = rand() % MAX_VALUE;
+
+    if (table.search(r->key) != nullptr) {
+      --i;
+      continue;
+    }
+
+    std::cout << "Inserting: Key => " << r->key << ", Value =>" << r->value << "\n";
+    table.insert(r);
+  }
+
+  // TEST: search & remove.
+  pRecord tmp;
+  for (int i = 0; i < MAX_VALUE; ++i) {
+    if ((tmp = table.search(i)) != nullptr) {
+      std::cout << "Deleting: Key => " << tmp->key << ", Value => " << tmp->value << "\n";
+      table.remove(tmp->key);
+    }
+  }
+
+  return 0;
+}

DataStructure/Hash/hash_table.hpp

@@ -0,0 +1,75 @@
+/*
+ * hash_table.hpp
+ * Copyright (C) 2019 Guowei Chen <[email protected]>
+ *
+ * Distributed under terms of the MIT license.
+ */
+
+#ifndef _HASH_TABLE_HPP_
+#define _HASH_TABLE_HPP_
+
+struct Record {
+  int key;
+  int value;
+};
+
+typedef Record * pRecord;
+
+class hash_table {
+public:
+  hash_table() {
+    for (int i = 0; i < MAX_SIZE; ++i) {
+      table[i] = nullptr;
+    }
+  }
+
+  // TODO: release  the memory.
+  ~hash_table() {}
+
+  // NOTE: insert operation.
+  void insert(pRecord r) {
+    if (r == nullptr) return ;
+
+    int i = hash(r->key);
+    while (table[i] != nullptr) {
+      i = (i + 1) % MAX_SIZE;
+    }
+    table[i] = r;
+  }
+
+  // NOTE: search
+  pRecord search(int key) {
+    int i = key;
+    while (table[ hash(i) ] != nullptr && table[ hash(i) ]->key != key) {
+      i = (i + 1) % MAX_SIZE;
+    }
+    return table[ hash(i) ];
+  }
+
+  // NOTE: remove
+  void remove(int key) {
+    int i = key;
+    while (table[ hash(i) ] != nullptr && table[ hash(i) ]->key != key) {
+      i = (i + 1) % MAX_SIZE;
+    }
+
+    table[ hash(i) ] = nullptr;
+
+    for (i = (i + 1) % MAX_SIZE ; table[ hash(i) ] != nullptr; i = (i + 1) % MAX_SIZE) {
+      insert(table[ hash(i) ]);
+      table[ hash(i) ] = nullptr;
+    }
+  }
+
+private:
+  static constexpr int MAX_SIZE = 97;
+
+  pRecord table[ MAX_SIZE ];
+
+  // NOTE: hash function.
+  int hash(int key) {
+    return (key % MAX_SIZE);
+  }
+};
+
+#endif // ifndef _HASH_TABLE_HPP_