diff --git a/search/hash_search.cpp b/search/hash_search.cpp
index 94d87b58a..6e4caffc3 100644
--- a/search/hash_search.cpp
+++ b/search/hash_search.cpp
@@ -1,100 +1,139 @@
-// Copyright 2020 Arctic2333
-#include <stdlib.h>
-#include<stdio.h>
-#define MAX 6  // Determines how much data
-# define HASHMAX 5  // Determines the length of the hash table
 /**
-  * Hash Search Algorithm
-  * Best Time Complexity Ω(1)
-  * In this algorithm, we use the method of division and reservation remainder to construct the hash function, 
-  * and use the method of chain address to solve the conflict, that is, we link a chain list after the data, 
-  * and store all the records whose keywords are synonyms in the same linear chain list. */
-int data[MAX] = { 1, 10, 15, 5, 8, 7};  // test data
+ * \file
+ * \brief Hash Search Algorithm - Best Time Complexity Ω(1)
+ *
+ * \copyright 2020 Arctic2333
+ *
+ * In this algorithm, we use the method of division and reservation remainder to
+ * construct the hash function, and use the method of chain address to solve the
+ * conflict, that is, we link a chain list after the data, and store all the
+ * records whose keywords are synonyms in the same linear chain list.
+ *
+ * @warning This program is only for educational purposes. It has serious flaws
+ * in implementation with regards to memory management resulting in large
+ * amounts of memory leaks.
+ * @todo fix the program for memory leaks and better structure in C++ and not C
+ * fashion
+ */
+#include <cstdlib>
+#include <iostream>
+
+#define MAX 6      ///< Determines how much data
+#define HASHMAX 5  ///< Determines the length of the hash table
+
+int data[MAX] = {1, 10, 15, 5, 8, 7};  //!< test data
+
+/**
+ * a one-way linked list
+ */
 typedef struct list {
-    int key;
-    struct list * next;
-}
-node, * link;
-node hashtab[HASHMAX];
-int counter = 1;
-/* int h(int key)
+    int key;            //!< key value for node
+    struct list* next;  //!< pointer to next link in the chain
+} node,                 /**< define node as one item list */
+    *link;              ///< pointer to nodes
+
+node hashtab[HASHMAX];  ///< array of nodes
+
+// int counter = 1;
+
+/**
  * Mode of hash detection :
- * Division method */
-int h(int key) {
-    return key % HASHMAX;
-}
-/* void create_list(int key)
+ * Division method
+ * \param [in] key to hash
+ * \returns hash value for `key`
+ */
+int h(int key) { return key % HASHMAX; }
+
+/**
  * The same after the remainder will be added after the same hash header
  * To avoid conflict, zipper method is used
- * Insert elements into the linked list in the header */
+ * Insert elements into the linked list in the header
+ * \param [in] key key to add to list
+ * \warning dynamic memory allocated to `n` never gets freed.
+ * \todo fix memory leak
+ */
 void create_list(int key) {  // Construct hash table
     link p, n;
     int index;
-    n = (link) malloc(sizeof(node));
-    n -> key = key;
-    n -> next = NULL;
+    n = (link)malloc(sizeof(node));
+    n->key = key;
+    n->next = NULL;
     index = h(key);
     p = hashtab[index].next;
     if (p != NULL) {
-        n -> next = p;
+        n->next = p;
         hashtab[index].next = n;
     } else {
-        hashtab[index].next = n; }
+        hashtab[index].next = n;
+    }
 }
-/* int hash_search(int key)
- * Input the key to be searched, and get the hash header position through the H (int key) function,
- * then one-dimensional linear search.
- * If found @return element depth and number of searches
- * If not found @return -1 */
-int hash_search(int key) {  // Hash lookup function
+
+/**
+ * Input the key to be searched, and get the hash header position through the H
+ * (int key) function, then one-dimensional linear search. If found @return
+ * element depth and number of searches If not found @return -1
+ */
+int hash_search(int key, int* counter) {  // Hash lookup function
     link pointer;
     int index;
-    counter = 0;
+
+    *counter = 0;
     index = h(key);
     pointer = hashtab[index].next;
-    printf("data[%d]:", index);
+
+    std::cout << "data[" << index << "]:";
+
     while (pointer != NULL) {
-        counter++;
-        printf("data[%d]:", pointer -> key);
-        if (pointer -> key == key)
+        counter[0]++;
+        std::cout << "data[" << pointer->key << "]:";
+        if (pointer->key == key)
             return 1;
         else
-            pointer = pointer -> next;
+            pointer = pointer->next;
     }
+
     return 0;
 }
+
+/** main function */
 int main() {
     link p;
-    int key, index, i;  // Key is the value to be found
+    int key, index, i, counter;  // Key is the value to be found
     index = 0;
+
     // You can write the input mode here
     while (index < MAX) {  // Construct hash table
         create_list(data[index]);
         index++;
     }
+
     for (i = 0; i < HASHMAX; i++) {  // Output hash table
-        printf("hashtab [%d]", i);
-        printf("\n");
+        std::cout << "hashtab [" << i << "]\n";
+
         p = hashtab[i].next;
+
         while (p != NULL) {
-            printf("please int key:");
-            if (p -> key > 0)
-                printf("[%d]", p -> key);
-            p = p -> next;
+            std::cout << "please int key:";
+            if (p->key > 0)
+                std::cout << "[" << p->key << "]";
+            p = p->next;
         }
-        printf("\n");
+        std::cout << std::endl;
     }
+
     while (key != -1) {
         // You can write the input mode here
         // test key = 10
         key = 10;
-        if (hash_search(key))
-            printf("search time = %d\n", counter);
+        if (hash_search(key, &counter))
+            std::cout << "search time = " << counter << std::endl;
         else
-            printf("no found!\n");
+            std::cout << "no found!\n";
         key = -1;  // Exit test
-        /* The test sample is returned as: data[0]:data[5]:data[15]:data[10]:search time = 3
-         * The search is successful. There are 10 in this set of data */
+        /* The test sample is returned as:
+         * data[0]:data[5]:data[15]:data[10]:search time = 3 The search is
+         * successful. There are 10 in this set of data */
     }
+
     return 0;
 }