Here's a new idea for implementing the sequence class from section 3.2. Instead of the items being stored on a linked list they will be stored using two stacks as private member variables with the following:

1. The bottom of the first stack is the beginning of the sequence.

2. The elements of the sequence continue up to the top of the first stack.

3. The next element of the sequence is then the top of the second stack.

4. And the elements of the sequence is then the top of the sequence then continues down to the bottom of the second sequence (which is the end of the sequence)

5. If there is a current element, then that element is at the top of the first stack.

You should delete the CAPACITY constant, but don't change any of the prototypes for any of the public member functions.

All of the public memeber functions should take constant time with one exception. Which one takes linear time?

NOTE: If you use a correctly written stack class for your two private memeber variables, then you do not need to write you own assignment operator, copy constructor or destructor. The reason for this is that C++ provides automatic versions of all three of these items, and the automatic versions call the respective functions for each of the member variables of the new class.

deque.h

#ifndef _DEQUE_H_ #define _DEQUE_H_

#include #include #include "node2.h"

using namespace main_savitch_6B;

template class deque { public: typedef std::size_t size_type; deque(); ~deque(); deque(const deque& dq); deque& operator = (const deque& dq); T& front(); T front() const; T& back(); T back() const; void push_front (const T& entry); void push_back (const T& entry); void pop_front(); void pop_back(); size_type size() const; bool empty() const; template friend bool operator == (const deque& dq1, const deque& dq2);

template friend std::ostream& operator<< (std::ostream& out, const deque& dq);

private: size_type count; // Total number of items in the queue node* first; node* last; };

#include "deque.template"

#endif

---------------------------------------------------------------------------------------------------------

******* Sequence.h ********

#ifndef _STACK_SEQUENCE_H_ #define _STACK_SAVITCH_SEQUENCE_H_ #include // Provides size_t #include namespace stack_sequence_4 { template class sequence { public: // TYPEDEFS and MEMBER CONSTANTS typedef std::size_t size_type; // CONSTRUCTOR sequence( ); // MODIFICATION MEMBER FUNCTIONS void start( ); void advance( ); void insert(const T& entry); void attach(const T& entry); void remove_current( ); // CONSTANT MEMBER FUNCTIONS size_type size( ) const; bool is_item( ) const; T current( ) const; private: std::stack first; std::stack second; }; }

#include "sequence4.template" #endif

============================================================================

********* Sequence_Exam.cpp ***********

// FILE: sequenceexam.cxx // Written by: Michael Main (main@colorado.edu) - Oct 22, 1997 // Non-interactive test program for the sequence class from Section 3.2 of // "Data Structures and Other Objects". // // Each function of this program tests part of the sequence class, returning // some number of points to indicate how much of the test was passed. // A description and result of each test is printed to cout. // // Maximum number of points awarded by this program is determined by the // constants POINTS[1], POINTS[2]...

#include // Provides cout. #include // Provides size_t. #include "sequence4.h" // Provides the sequence class with double items. using namespace std; using namespace stack_sequence_4;

// Descriptions and points for each of the tests: const size_t MANY_TESTS = 3; const int POINTS[MANY_TESTS+1] = { 100, // Total points for all tests. 50, // Test 1 points 25, // Test 2 points 25 // Test 3 points }; const char DESCRIPTION[MANY_TESTS+1][256] = { "tests for Chapter 3 sequence Class", "Testing insert, attach, and the constant member functions", "Testing situations where the cursor goes off the sequence", "Testing remove_current" };

// ************************************************************************** // bool test_basic(const sequence& test, size_t s, bool has_cursor) // Postcondition: A return value of true indicates: // a. test.size() is s, and // b. test.is_item() is has_cursor. // Otherwise the return value is false. // In either case, a description of the test result is printed to cout. // ************************************************************************** bool test_basic(const sequence& test, size_t s, bool has_cursor) { bool answer;

cout << "Testing that size() returns " << s << " ... "; cout.flush( ); answer = (test.size( ) == s); cout << (answer ? "Passed." : "Failed.") << endl; if (answer) { cout << "Testing that is_item() returns "; cout << (has_cursor ? "true" : "false") << " ... "; cout.flush( ); answer = (test.is_item( ) == has_cursor); cout << (answer ? "Passed." : "Failed.") << endl; }

return answer; }

// ************************************************************************** // bool test_items(sequence& test, size_t s, size_t i, double items[]) // The function determines if the test sequence has the correct items // Precondition: The size of the items array is at least s. // Postcondition: A return value of true indicates that test.current() // is equal to items[i], and after test.advance() the result of // test.current() is items[i+1], and so on through items[s-1]. // At this point, one more advance takes the cursor off the sequence. // If any of this fails, the return value is false. // NOTE: The test sequence has been changed by advancing its cursor. // ************************************************************************** bool test_items(sequence& test, size_t s, size_t i, double items[]) { bool answer = true; cout << "The cursor should be at item [" << i << "]" << " of the sequence "; cout << "(counting the first item as [0]). I will advance the cursor "; cout << "to the end of the sequence, checking that each item is correct..."; cout.flush( ); while ((i < s) && test.is_item( ) && (test.current( ) == items[i])) { i++; test.advance( ); }

if ((i != s) && !test.is_item( )) { // The test.is_item( ) function returns false too soon. cout << " Cursor fell off the sequence too soon." << endl; answer = false; } else if (i != s) { // The test.current( ) function returned a wrong value. cout << " The item [" << i << "] should be " << items[i] << ", "; cout << " but it was " << test.current( ) << " instead. "; answer = false; } else if (test.is_item( )) { // The test.is_item( ) function returns true after moving off the sequence. cout << " The cursor was moved off the sequence,"; cout << " but is_item still returns true." << endl; answer = false; }

cout << (answer ? "Passed." : "Failed.") << endl; return answer; }

// ************************************************************************** // bool correct(sequence test, size_t s, size_t cursor_spot, double items[]) // This function determines if the sequence (test) is "correct" according to // these requirements: // a. it has exactly s items. // b. the items (starting at the front) are equal to // double[0] ... double[size-1] // c. if cursor_spot < size, then test's cursor must be at // the location given by cursor_spot. // d. if cursor_spot >= size, then test must not have a cursor. // NOTE: The function also moves the cursor off the sequence. // ************************************************************************** bool correct(sequence& test, size_t size, size_t cursor_spot, double items[]) { bool has_cursor = (cursor_spot < size);

// Check the sequence's size and whether it has a cursor. if (!test_basic(test, size, has_cursor)) { cout << "Basic test of size() or is_item() failed." << endl << endl; return false; }

// If there is a cursor, check the items from cursor to end of the sequence. if (has_cursor && !test_items(test, size, cursor_spot, items)) { cout << "Test of the sequence's items failed." << endl << endl; return false; }

// Restart the cursor at the front of the sequence and test items again. cout << "I'll call start() and look at the items one more time..." << endl; test.start( ); if (has_cursor && !test_items(test, size, 0, items)) { cout << "Test of the sequence's items failed." << endl << endl; return false; }

// If the code reaches here, then all tests have been passed. cout << "All tests passed for this sequence." << endl << endl; return true; }

// ************************************************************************** // int test1( ) // Performs some basic tests of insert, attach, and the constant member // functions. Returns POINTS[1] if the tests are passed. Otherwise returns 0. // ************************************************************************** int test1( ) { sequence empty; // An empty sequence sequence test; // A sequence to add items to double items1[4] = { 5, 10, 20, 30 }; // These 4 items are put in a sequence double items2[4] = { 10, 15, 20, 30 }; // These are put in another sequence

// Test that the empty sequence is really empty cout << "Starting with an empty sequence." << endl; if (!correct(empty, 0, 0, items1)) return 0;

// Test the attach function to add something to an empty sequence cout << "I am now using attach to put 10 into an empty sequence." << endl; test.attach(10); if (!correct(test, 1, 0, items2)) return 0; // Test the insert function to add something to an empty sequence cout << "I am now using insert to put 10 into an empty sequence." << endl; test = empty; test.insert(10); if (!correct(test, 1, 0, items2)) return 0; // Test the insert function to add an item at the front of a sequence cout << "I am now using attach to put 10,20,30 in an empty sequence. "; cout << "Then I move the cursor to the start and insert 5." << endl; test = empty; test.attach(10); test.attach(20); test.attach(30); test.start( ); test.insert(5); if (!correct(test, 4, 0, items1)) return 0; // Test the insert function to add an item in the middle of a sequence cout << "I am now using attach to put 10,20,30 in an empty sequence. "; cout << "Then I move the cursor to the start, advance once, "; cout << "and insert 15." << endl; test = empty; test.attach(10); test.attach(20); test.attach(30); test.start( ); test.advance( ); test.insert(15); if (!correct(test, 4, 1, items2)) return 0;

// Test the attach function to add an item in the middle of a sequence cout << "I am now using attach to put 10,20,30 in an empty sequence. "; cout << "Then I move the cursor to the start and attach 15 "; cout << "after the 10." << endl; test = empty; test.attach(10); test.attach(20); test.attach(30); test.start( ); test.attach(15); if (!correct(test, 4, 1, items2)) return 0;

// All tests have been passed cout << "All tests of this first function have been passed." << endl; return POINTS[1]; }

// ************************************************************************** // int test2( ) // Performs a test to ensure that the cursor can correctly be run off the end // of the sequence. Also tests that attach/insert work correctly when there is // no cursor. Returns POINTS[2] if the tests are passed. Otherwise returns 0. // ************************************************************************** int test2( ) { sequence test; size_t i;

// Put three items in the sequence cout << "Using attach to put 20 and 30 in the sequence, and then calling "; cout << "advance, so that is_item should return false ... "; cout.flush( ); test.attach(20); test.attach(30); test.advance( ); if (test.is_item( )) { cout << "failed." << endl; return 0; } cout << "passed." << endl;

// Insert 10 at the front and run the cursor off the end again cout << "Inserting 10, which should go at the sequence's front." << endl; cout << "Then calling advance three times to run cursor off the sequence ..."; cout.flush( ); test.insert(10); test.advance( ); // advance to the 20 test.advance( ); // advance to the 30 test.advance( ); // advance right off the sequence if (test.is_item( )) { cout << " failed." << endl; return false; } cout << " passed." << endl; /* // Attach more items until the sequence becomes full. // Note that the first attach should attach to the end of the sequence. cout << "Calling attach to put the numbers 40, 50, 60 ..."; cout << test.CAPACITY*10 << " at the sequence's end." << endl; for (i = 4; i <= test.CAPACITY; i++) test.attach(i*10);

// Test that the sequence is correctly filled. cout << "Now I will test that the sequence has 10, 20, 30, ..."; cout << test.CAPACITY*10 << "." << endl; test.start( ); for (i = 1; i <= test.CAPACITY; i++) { if ((!test.is_item( )) || test.current( ) != i*10) { cout << " Test failed to find " << i*10 << endl; return 0; } test.advance( ); } if (test.is_item( )) { cout << " There are too many items on the sequence." << endl; return false; } */ // All tests passed cout << "All tests of this second function have been passed." << endl; return POINTS[2]; }

// ************************************************************************** // int test3( ) // Performs basic tests for the remove_current function. // Returns POINTS[3] if the tests are passed. Returns POINTS[3] / 4 if almost // all the tests are passed. Otherwise returns 0. // ************************************************************************** int test3( ) { // In the next declarations, I am declaring a sequence called test. // Both before and after the sequence, I declare a small array of characters, // and I put the character 'x' into each spot of these arrays. // Later, if I notice that one of the x's has been changed, or if // I notice an 'x' inside of the sequence, then the most // likely reason was that one of the sequence's member functions accessed // the sequence's array outside of its legal indexes. char prefix[4] = {'x', 'x', 'x', 'x'}; sequence test; char suffix[4] = {'x', 'x', 'x', 'x'};

// Within this function, I create several different sequences using the // items in these arrays: double items1[1] = { 30 }; double items2[2] = { 10, 30 }; double items3[3] = { 10, 20, 30 }; size_t i; // for-loop control variable char *char_ptr; // Variable to loop at each character in a sequence's memory

// Build a sequence with three items 10, 20, 30, and remove the middle, // and last and then first. cout << "Using attach to build a sequence with 10,30." << endl; test.attach(10); test.attach(30); cout << "Insert a 20 before the 30, so entire sequence is 10,20,30." << endl; test.insert(20); if (!correct(test, 3, 1, items3)) return 0; cout << "Remove the 20, so entire sequence is now 10,30." << endl; test.start( ); test.advance( ); test.remove_current( ); if (!correct(test, 2, 1, items2)) return 0; cout << "Remove the 30, so entire sequence is now just 10 with no cursor."; cout << endl; test.start( ); test.advance( ); test.remove_current( ); if (!correct(test, 1, 1, items2)) return 0; cout << "Set the cursor to the start and remove the 10." << endl; test.start( ); test.remove_current( ); if (!correct(test, 0, 0, items2)) return 0;

// Build a sequence with three items 10, 20, 30, and remove the middle, // and then first and then last. cout << "Using attach to build another sequence with 10,30." << endl; test.attach(10); test.attach(30); cout << "Insert a 20 before the 30, so entire sequence is 10,20,30." << endl; test.insert(20); if (!correct(test, 3, 1, items3)) return 0; cout << "Remove the 20, so entire sequence is now 10,30." << endl; test.start( ); test.advance( ); test.remove_current( ); if (!correct(test, 2, 1, items2)) return 0; cout << "Set the cursor to the start and remove the 10," << endl; cout << "so the sequence should now contain just 30." << endl; test.start( ); test.remove_current( ); if (!correct(test, 1, 0, items1)) return 0; cout << "Remove the 30 from the sequence, resulting in an empty sequence." << endl; test.start( ); test.remove_current( ); if (!correct(test, 0, 0, items1)) return 0;

// Build a sequence with three items 10, 20, 30, and remove the first. cout << "Build a new sequence by inserting 30, 10, 20 (so the sequence "; cout << "is 20, then 10, then 30). Then remove the 20." << endl; test.insert(30); test.insert(10); test.insert(20); test.remove_current( ); if (!correct(test, 2, 0, items2)) return 0; test.start( ); test.remove_current( ); test.remove_current( ); /* // Just for fun, fill up the sequence, and empty it! cout << "Just for fun, I'll empty the sequence then fill it up, then "; cout << "empty it again. During this process, I'll try to determine "; cout << "whether any of the sequence's member functions access the "; cout << "array outside of its legal indexes." << endl; for (i = 0; i < test.CAPACITY; i++) test.insert(0); for (i = 0; i < test.CAPACITY; i++) test.remove_current( );

// Make sure that the character 'x' didn't somehow get into the sequence, // as that would indicate that the sequence member functions are // copying data from before or after the sequence into the sequence. char_ptr = (char *) &test; for (i = 0; i < sizeof(sequence); i++) if (char_ptr[i] == 'x') { cout << "Illegal array access detected." << endl; return POINTS[3] / 4; } */ // Make sure that the prefix and suffix arrays still have four // x's each. Otherwise one of the sequence operations wrote outside of // the legal boundaries of its array. for (i = 0; i < 4; i++) if ((suffix[i] != 'x') || (prefix[i] != 'x')) { cout << "Illegal array access detected." << endl; return POINTS[3] / 4; } // All tests passed cout << "All tests of this third function have been passed." << endl; return POINTS[3]; }

int run_a_test(int number, const char message[], int test_function( ), int max) { int result; cout << endl << "START OF TEST " << number << ":" << endl; cout << message << " (" << max << " points)." << endl; result = test_function( ); if (result > 0) { cout << "Test " << number << " got " << result << " points"; cout << " out of a possible " << max << "." << endl; } else cout << "Test " << number << " failed." << endl; cout << "END OF TEST " << number << "." << endl << endl; return result; }

// ************************************************************************** // int main( ) // The main program calls all tests and prints the sum of all points // earned from the tests. // ************************************************************************** int main( ) { int sum = 0; cout << "Running " << DESCRIPTION[0] << endl;

sum += run_a_test(1, DESCRIPTION[1], test1, POINTS[1]); sum += run_a_test(2, DESCRIPTION[2], test2, POINTS[2]); sum += run_a_test(3, DESCRIPTION[3], test3, POINTS[3]);

cout << "If you submit the Chapter 3 sequence to Dora now, you will have "; cout << sum << " points out of the " << POINTS[0]; cout << " points from this test program. "; return EXIT_SUCCESS;

}

---------------------------------------------------------------------------------------------------------

********* node2.h ************

#ifndef MAIN_SAVITCH_NODE2_H #define MAIN_SAVITCH_NODE2_H #include  // Provides NULL and size_t #include  // Provides iterator and forward_iterator_tag namespace main_savitch_6B { template  class node { public: // TYPEDEF typedef Item value_type; // CONSTRUCTOR node(const Item& init_data=Item( ), node* init_link=NULL) { data_field = init_data; link_field = init_link; } // MODIFICATION MEMBER FUNCTIONS Item& data( ) { return data_field; } node* link( ) { return link_field; } void set_data(const Item& new_data) { data_field = new_data; } void set_link(node* new_link) { link_field = new_link; } // CONST MEMBER FUNCTIONS const Item& data( ) const { return data_field; } const node* link( ) const { return link_field; } private: Item data_field; node *link_field; }; // FUNCTIONS to manipulate a linked list: template  void list_clear(node*& head_ptr); template  void list_copy (const node* source_ptr, node*& head_ptr, node*& tail_ptr); template  void list_head_insert(node*& head_ptr, const Item& entry); template  void list_head_remove(node*& head_ptr); template  void list_insert(node* previous_ptr, const Item& entry); template  std::size_t list_length(const node* head_ptr); template  NodePtr list_locate(NodePtr head_ptr, SizeType position); template  void list_remove(node* previous_ptr); template  NodePtr list_search(NodePtr head_ptr, const Item& target); // FORWARD ITERATORS to step through the nodes of a linked list // A node_iterator of can change the underlying linked list through the // * operator, so it may not be used with a const node. The // node_const_iterator cannot change the underlying linked list // through the * operator, so it may be used with a const node. // WARNING: // This classes use std::iterator as its base class; // Older compilers that do not support the std::iterator class can // delete everything after the word iterator in the second line: template  class node_iterator : public std::iterator { public: node_iterator(node* initial = NULL) { current = initial; } Item& operator *( ) const { return current->data( ); } node_iterator& operator ++( ) // Prefix ++ { current = current->link( ); return *this; } node_iterator operator ++(int) // Postfix ++ { node_iterator original(current); current = current->link( ); return original; } bool operator ==(const node_iterator other) const { return current == other.current; } bool operator !=(const node_iterator other) const { return current != other.current; } private: node* current; }; template  class const_node_iterator : public std::iterator { public: const_node_iterator(const node* initial = NULL) { current = initial; } const Item& operator *( ) const { return current->data( ); } const_node_iterator& operator ++( ) // Prefix ++ { current = current->link( ); return *this; } const_node_iterator operator ++(int) // Postfix ++ { const_node_iterator original(current); current = current->link( ); return original; } bool operator ==(const const_node_iterator other) const { return current == other.current; } bool operator !=(const const_node_iterator other) const { return current != other.current; } private: const node* current; }; } #include "node2.template" #endif