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Author: anserwaseem

hashMap.cpp

@@ -0,0 +1,203 @@
+#include<iostream>
+#include<cassert>
+#include<fstream>
+#include<string>
+#include<sstream>
+using namespace std;
+
+template <class v>
+struct HashItem
+{
+    int key;
+    v value;
+    short int status;
+};
+
+template <class v>
+class HashMap
+{
+protected:
+    HashItem<v>* hashArray;
+    int capacity;
+    int currentElements;
+    void doubleCapacity()
+    {
+        int oldCapacity = capacity;
+        this->capacity = capacity*2;
+        HashItem<v>* newHashArray = new HashItem<v> [capacity] ();
+
+        cout<<endl<<"Doubling the capacity from "<<oldCapacity<<" to "<<this->capacity<<" and rearranging all the key value pairs.\n";
+        for(int i=0; i<oldCapacity; i++)
+            if(hashArray[i].status==2)//if occupied
+                insert_helper(hashArray[i].key, hashArray[i].value, newHashArray);
+        
+        this->hashArray=newHashArray;
+        newHashArray = nullptr;
+    }
+    virtual int getNextCandidateIndex(int key, int i, HashItem<v>* hashArr)
+    {
+        int index = (key+i)%capacity;
+        if(hashArr[index].status==0)//if this next candidate index is free, then send its index number or check for the next one
+            return index;
+        return getNextCandidateIndex(key, ++i, hashArr);
+    }
+    void insert_helper(int const key, v const value, HashItem<v>* arr)
+    {
+        int index = key%capacity;
+
+        if (arr[index].status==2)//if occupied
+            index = getNextCandidateIndex(key, 1, arr);
+
+        arr[index].key=key;
+        arr[index].value=value;
+        arr[index].status=2;//occupied
+        cout<<"index: "<<index<<"    ,key: "<<key<<"    ,value: "<<value<<endl;
+    }
+public:
+    HashMap()
+    {
+        capacity = 7;//prime number
+        currentElements = 0;
+        hashArray = new HashItem<v> [capacity] ();
+    }
+    HashMap(int const _capacity)
+    {
+        assert(capacity>1);
+        capacity = _capacity;
+        currentElements = 0;
+        hashArray = new HashItem<v> [capacity] ();
+    }
+    HashItem<v>* getHashArray()
+    {
+        return this->hashArray;
+    }
+    void insert(int const key, v const value, HashItem<v>* hashArr)
+    {
+        if( ( ((float)(currentElements)) / ((float)(capacity)) ) >= 0.75 )//load factor
+            doubleCapacity();
+
+        insert_helper(key, value, hashArr);
+
+        currentElements++;
+    }
+    bool deleteKey(int const key) const
+    {
+        for(int i=0; i<this->capacity; i++)
+            if(hashArray[i].key == key)
+            {
+                hashArray[i].status = 1;//key deleted
+                cout<<key<<" deleted.\n";
+                return true;
+            }
+
+        cout<<"key not found.\n";
+        return false;
+    }
+    v* get(int const key) const
+    {
+        for(int i=0; i<this->capacity; i++)
+            if(hashArray[i].key == key)
+            {
+                cout<<"key found at index"<<i<<endl;
+                return (&hashArray[i].value);
+            }
+
+        cout<<"key not found.\n";
+        return nullptr;
+    }
+    ~HashMap()
+    {
+        if(hashArray!=nullptr)
+            hashArray=nullptr;
+        delete hashArray;
+    }
+};
+
+template<class v>
+class QHashMap : public HashMap<v>
+{
+public:
+    int getNextCandidateIndex(int key, int i, HashItem<v>* hashArr)
+    {
+        // int _key = (key + (i*i));
+        // if(_key<0)
+        //     _key+=this->capacity;
+
+        int index = (key + (i*i)) % this->capacity;
+        if(hashArr[index].status==0)//if free
+            return index;
+        return getNextCandidateIndex(key, ++i, hashArr);
+    }
+};
+
+template<class v>
+class DHashMap : public HashMap<v>
+{
+public:
+    int getNextCandidateIndex(int key, int i, HashItem<v>* hashArr)
+    {
+        int first_value = key % this->capacity;
+        int second_value = 7 - (key % 7);
+        int candidate_index = (first_value + (i*second_value)) % this->capacity;
+
+        if(hashArr[candidate_index].status==0)//if free
+            return candidate_index;
+        return getNextCandidateIndex(key, ++i, hashArr);
+    }
+};
+
+void populateHash(string filename, HashMap<string> *hash)
+{
+    ifstream fin;
+    fin.open(filename);
+    int Tsize;
+    fin>>Tsize;
+    fin.ignore();
+
+    while(Tsize>0)
+    {
+        string name;
+        getline(fin, name);
+
+        int att = name.find(' ');
+        string _key = name.substr(0, att);
+        //int id = stoi(_key, nullptr, 10);
+        stringstream id(_key);
+        int ID=0;
+        id>>ID;
+
+        name=name.substr(att+1, name.size());
+
+        hash->insert(ID, name, hash->getHashArray());
+
+        Tsize--;
+    }
+}
+int main()
+{
+    cout<<"LINEAR PROBING\n";
+    HashMap<string> *map=new HashMap<string>;
+    populateHash("students.txt", map);
+    cout<<"Calling get function:\t"<<*map->get(9)<<endl<<endl;
+    cout<<"Calling deleteKey function:\t";map->deleteKey(9);cout<<endl;
+    //assert((map->get(9)==nullptr));
+    free (map);
+
+    cout<<"QUADRATIC PROBING\n";
+    QHashMap<string> *Qmap=new QHashMap<string>;
+    populateHash("students.txt", Qmap);
+    cout<<"Calling get function:\t"<<*Qmap->get(9)<<endl<<endl;
+    cout<<"Calling deleteKey function:\t";Qmap->deleteKey(9);cout<<endl;
+    //assert(Qmap->get(9)==nullptr);
+    free (Qmap);
+
+    cout<<"DOUBLE HASHING\n";
+    DHashMap<string> *Dmap=new DHashMap<string>;
+    populateHash("students.txt", Dmap);
+    cout<<"Calling get function:\t"<<*Dmap->get(9)<<endl<<endl;
+    cout<<"Calling deleteKey function:\t";Dmap->deleteKey(9);cout<<endl;
+    //assert(Dmap->get(9)==nullptr);
+    free (Dmap);
+
+    return 0;
+}

students.txt

@@ -0,0 +1,19 @@
+18
+9 Akram
+254 Yaseen
+111 Abdul
+6 Momin
+5 Ali
+4 Farooq
+176 Danial
+101 Ibtissam
+153 Zayd
+10 Tania
+16 Ahmed
+300 Ahmed
+43 Umer
+15 Haroon
+98 Nimra
+1 Tariq
+2 Umer
+3 Ali