9.13 Lab: Hashing - Linear Probe (insert, search, delete)

Reuse code from the previous lab and write new code as described below:

- search hash: Modify this function to return -1 if the target key is not found or the number of collisions for that key if found.

`int search(Student &target, string key);`

- remove hash: Create a new function to delete an item from the hash table.
- insert manager: inserts user provided data into the hash table and rejects duplicates.

06-hash-tables/HashTable.cpp

@@ -27,7 +27,7 @@ bool HashTable::insert(const Student &itemIn) {
         return false;
     int pos = _hash(itemIn.getName());
     int collisions = 0;
-    while (hashAry[pos].getOccupied()) {
+    while (hashAry[pos].getOccupied() == 1) {
         ++pos;
         ++collisions;
         pos = pos % hashSize;
@@ -43,7 +43,18 @@ bool HashTable::insert(const Student &itemIn) {
 /*~*~*~*
    hash delete - linear probe
 *~**/
-bool HashTable::remove(Student &itemOut) {
+bool HashTable::remove(Student &itemOut, string key) {
+    int pos = _hash(key);
+    for (int collisions = 0; collisions < count; collisions++) {
+        if (hashAry[pos].getOccupied() == 1 && hashAry[pos].getItem().getName() == key) {
+            itemOut = hashAry[pos].getItem();
+            // -1 means freed
+            hashAry[pos].setOccupied(-1);
+            count--;
+            return true;
+        }
+        pos = (pos + 1) % hashSize;
+    }
     return false;
 }
 
@@ -56,16 +67,15 @@ bool HashTable::remove(Student &itemOut) {
       - returns true
    if not found, returns false
 *~**/
-bool HashTable::search(Student &itemOut, int &noCol, string key) {
+int HashTable::search(Student &itemOut, string key) const {
     int pos = _hash(key);
     for (int collisions = 0; collisions < count; collisions++) {
-        if (!hashAry[pos].getOccupied()) return false;
-        if (hashAry[pos].getItem().getName() == key) {
+        if (hashAry[pos].getOccupied() == 0) return -1;
+        if (hashAry[pos].getOccupied() == 1 && hashAry[pos].getItem().getName() == key) {
             itemOut = hashAry[pos].getItem();
-            noCol = hashAry[pos].getNoCollisions();
-            return true;
+            return hashAry[pos].getNoCollisions();
         }
         pos = (pos + 1) % hashSize;
     }
-    return false;
+    return -1;
 }

06-hash-tables/HashTable.h

@@ -40,9 +40,9 @@ public:
 
     bool insert(const Student &itemIn);
 
-    bool remove(Student &itemOut);
+    bool remove(Student &itemOut, string key);
 
-    bool search(Student &itemOut, int &noCol, string key);
+    int search(Student &itemOut, string key) const;
 
 private:
     int _hash(string key) const;

06-hash-tables/main.cpp

@@ -1,16 +1,12 @@
 /*
  CIS 22C
- 
- This program builds and searches a hash table.
-  
- Written by: Iurii Tatishchev
+ Hashing - Linear Probe: insert, search, and delete
+ Written By: Iurii Tatishchev
  Reviewed & Modified by: Iurii Tatishchev
- IDE: CLion
- 
- */
+*/
+
 #include <iostream>
 #include <sstream>
-#include <cctype>
 
 #include "HashTable.h"
 
@@ -18,40 +14,47 @@ using namespace std;
 
 void buildHash(HashTable &hash);
 
-void searchManager(HashTable &hash);
+void searchManager(const HashTable &hash);
+
+void deleteManager(HashTable &hash);
+
+void insertManager(HashTable &hash);
 
 int main() {
     HashTable hash;
-    string option;
 
     buildHash(hash);
-
     cout << "Load Factor: " << hash.getLoadFactor() << endl;
-
     searchManager(hash);
+    deleteManager(hash);
+    insertManager(hash);
 
     return 0;
 }
 
 /* **************************************************
-This function builds a hash table with data from the keyboard.
+This function builds a hash table with data from an array
 It calls the insert() function that inserts the new data at the right location in the hash table.
-An input line contains the gpa of a student follow by name (assume it is a single word name)
-To stop reading enter "#"
 ************************************************** */
 void buildHash(HashTable &hash) {
-    string line;
-    cout << "Enter gpa and name [# to stop reading]:" << endl;
-    getline(cin, line);
-    while (line != "#") {
-        stringstream temp(line); // create a stringstream named temp with data from line
-        double gpa;
-        string name;
-        temp >> gpa;  // read gpa from temp
-        temp >> name; // read name from temp
-        Student newStu(name, gpa);
-        hash.insert(newStu);
-        getline(cin, line);
+
+    Student list[] = {{"Tom",   2.5},
+                      {"Bob",   3.2},
+                      {"Boc",   3.2},
+                      {"Linda", 3.9},
+                      {"Tim",   4.0},
+                      {"Vic",   3.9},
+                      {"Ann",   3.5},
+                      {"Dylan", 3.1},
+                      {"obB",   2.2},
+                      {"oBb",   3.7},
+                      {"Bbo",   3.3},
+                      {"bBo",   3.9},
+                      {"boB",   2.3},
+                      {"",      0}};
+
+    for (int i = 0; list[i].getName() != ""; i++) {
+        hash.insert(list[i]);
     }
 
 }
@@ -61,19 +64,71 @@ This function searches a hash table with user provided data.
 It calls the hash search function in a loop.
 To stop searching enter "#"
 ************************************************** */
-void searchManager(HashTable &hash) {
-    string name;
+void searchManager(const HashTable &hash) {
+    cout << endl << "~*~ Test Search ~*~" << endl;
     cout << "Enter name [# to stop searching]:" << endl;
+    string name;
     getline(cin, name);
     while (name != "#") {
         Student item;
-        int nc;
-        if (hash.search(item, nc, name)) {
+        int nc = hash.search(item, name);
+        if (nc != -1) {
             cout << item.getName() << " " << item.getGpa() << " (" << nc << " collisions!)" << endl;
         } else {
             cout << name << " not found!" << endl;
         }
         getline(cin, name);
     }
-
+}
+
+/* **************************************************
+This function deletes user provided data data from a hash table
+It calls the hash delete function in a loop.
+To stop deleting enter "#"
+************************************************** */
+void deleteManager(HashTable &hash) {
+    cout << endl << "~*~ Test Delete ~*~" << endl;
+    cout << "Enter name [# to stop deleting]:" << endl;
+    string name;
+    getline(cin, name);
+    while (name != "#") {
+        Student itemOut;
+        if (hash.remove(itemOut, name)) {
+            cout << itemOut.getName() << " " << itemOut.getGpa() << " - deleted!" << endl;
+        } else {
+            cout << name << " not found!" << endl;
+        }
+        cout << "Load Factor: " << hash.getLoadFactor() << endl;
+        getline(cin, name);
+    }
+}
+
+/* **************************************************
+This function inserts user provided data into the hash table
+It rejects duplicates.
+It calls hash search and hash insert in a loop.
+To stop getting user input enter "#"
+************************************************** */
+void insertManager(HashTable &hash) {
+    cout << endl << "~*~ Test Insert - reject duplicates ~*~" << endl;
+    cout << "Enter name [# to stop reading]:" << endl;
+    string name;
+    getline(cin, name);
+    while (name != "#") {
+        Student found;
+        if (hash.search(found, name) != -1) {
+            cout << "Duplicate key: " << found.getName() << " - rejected!" << endl;
+        } else {
+            cout << "Enter gpa:" << endl;
+            double gpa;
+            cin >> gpa;
+            cin.ignore();
+            Student newStudent(name, gpa);
+            hash.insert(newStudent);
+            cout << name << " - inserted (" << hash.search(found, name) << " collisions)" << endl;
+        }
+        cout << "Load Factor: " << hash.getLoadFactor() << endl;
+        cout << "Enter name [# to stop reading]:" << endl;
+        getline(cin, name);
+    }
 }