# C++ > Data Structures and Algorithm Analysis in C++ Code Examples

``` Header file for quadratic probing hash table #ifndef QUADRATIC_PROBING_H_ #define QUADRATIC_PROBING_H_ #include "vector.h" #include "mystring.h" // QuadraticProbing Hash table class // // CONSTRUCTION: an initialization for ITEM_NOT_FOUND // and an approximate initial size or default of 101 // // ******************PUBLIC OPERATIONS********************* // void insert( x ) --> Insert x // void remove( x ) --> Remove x // Hashable find( x ) --> Return item that matches x // void makeEmpty( ) --> Remove all items template <class HashedObj> class HashTable { public: explicit HashTable( const HashedObj & notFound, int size = 101 ); HashTable( const HashTable & rhs ) : ITEM_NOT_FOUND( rhs.ITEM_NOT_FOUND ), array( rhs.array ), currentSize( rhs.currentSize ) { } const HashedObj & find( const HashedObj & x ) const; void makeEmpty( ); void insert( const HashedObj & x ); void remove( const HashedObj & x ); const HashTable & operator=( const HashTable & rhs ); enum EntryType { ACTIVE, EMPTY, DELETED }; private: struct HashEntry { HashedObj element; EntryType info; HashEntry( const HashedObj & e = HashedObj( ), EntryType i = EMPTY ) : element( e ), info( i ) { } }; vector<HashEntry> array; int currentSize; const HashedObj ITEM_NOT_FOUND; bool isActive( int currentPos ) const; int findPos( const HashedObj & x ) const; void rehash( ); }; int hash( const string & key, int tableSize ); int hash( int key, int tableSize ); #include "QuadraticProbing.cpp" #endif ```