212
Fundamentals UAH
CPE of Software Engineering Agenda Class 11 Linked Lists 2
Linked Lists Application Key Concepts
UAH
CPE 212
Today
Last Time
First Fundamental Structure, Linked Lists
This Time
Bagged Again
UAH
CPE 212
Linked List For Bag
#ifndef LINK1_H #define LINK1_H #include <stdlib.h> // Provides size_t
struct Node { typedef double Item; Item data; Node *link; };
// FUNCTIONS for the linked list toolkit size_t list_length(Node* head_ptr); void list_head_insert(Node*& head_ptr, const Node::Item& entry); void list_insert(Node* previous_ptr, const Node::Item& entry); Node* list_search(Node* head_ptr, const Node::Item& target); Node* list_locate(Node* head_ptr, size_t position); void list_head_remove(Node*& head_ptr); void list_remove(Node* previous_ptr); void list_clear(Node*& head_ptr); void list_copy(Node* source_ptr, Node*& head_ptr, Node*& tail_ptr); void list_piece(Node* start_ptr, Node* end_ptr, Node*& head_ptr, Node*& tail_ptr);
#endif
UAH
CPE 212
Bag 3
#ifndef BAG_H #define BAG_H #include <stdlib.h> // Provides size_t and NULL #include "link1.h" // Provides Node struct class Bag { public: // TYPEDEF typedef Node::Item Item; // CONSTRUCTORS and DESTRUCTOR Bag( ); Bag(const Bag& source); ~Bag( ); // MODIFICATION functions void insert(const Item& entry); void remove(const Item& target); void operator +=(const Bag& addend); void operator =(const Bag& source); // CONSTANT functions size_t size( ) const { return many_nodes; } size_t occurrences(const Item& target) const; Item grab( ) const; private: Node *head_ptr; // Head pointer for the list of items size_t many_nodes; // Number of nodes on the list }; //End of Class Bag // NONMEMBER functions for the Bag Bag operator +(const Bag& b1, const Bag& b2); #endif
UAH
CPE 212
Bag 3 2
// FILE: bag3.cxx // CLASS implemented: Bag (see bag3.h for documentation) // INVARIANT for the Bag ADT: // 1. The items in the Bag are stored on a linked list; // 2. The head pointer of the list is stored in the member variable head_ptr; // 3. The total number of items in the list is stored in the member variable // many_nodes. #include <assert.h> // Provides assert #include <stdlib.h> // Provides NULL, rand, size_t #include "link1.h" // Provides Node and the ten linked list functions #include "bag3.h" Bag::Bag( ) // Library facilities used: stdlib.h { head_ptr = NULL; many_nodes = 0; } Bag::Bag(const Bag& source) // Library facilities used: link1.h { Node *tail_ptr; // Needed for argument of list_copy
list_copy(source.head_ptr, head_ptr, tail_ptr); many_nodes = source.many_nodes;
} Bag::~Bag( ) // Library facilities used: link1.h { list_clear(head_ptr); many_nodes = 0; }
UAH
CPE 212
Bag 3 3
void Bag::operator =(const Bag& source) // Library facilities used: link1.h { Node *tail_ptr; // Needed for argument to list_copy
if (source.head_ptr == head_ptr) return; list_clear(head_ptr); many_nodes = 0;
list_copy(source.head_ptr, head_ptr, tail_ptr); many_nodes = source.many_nodes;
}
void Bag::remove(const Item& target) // Library facilities used: link1.h, stdlib.h { Node *target_ptr;
target_ptr = list_search(head_ptr, target); if (target == NULL) return; // target isn't in the Bag, so no work to do target_ptr->data = head_ptr->data; list_head_remove(head_ptr); many_nodes--;
}
UAH
CPE 212
Bag 3 4
void Bag::insert(const Item& entry) // Library facilities used: link1.h { list_head_insert(head_ptr, entry); many_nodes++; } void Bag::operator +=(const Bag& addend) // Library facilities used: stdlib.h { Node *copy_head_ptr; Node *copy_tail_ptr; if (addend.many_nodes > 0) { list_copy(addend.head_ptr, copy_head_ptr, copy_tail_ptr); copy_tail_ptr->link = head_ptr; head_ptr = copy_head_ptr; many_nodes += addend.many_nodes; } } Bag::Item Bag::grab( ) const // Library facilities used: assert.h, stdlib.h, link1.h { size_t i; Node *cursor; assert(size( ) > 0); i = (rand( ) % size( )) + 1; cursor = list_locate(head_ptr, i); return cursor->data; }
UAH
CPE 212
Bag 3 5
size_t Bag::occurrences(const Item& target) const // Library facilities used: stdlib.h, link1.h { size_t answer; Node *cursor;
answer = 0; cursor = list_search(head_ptr, target); while (cursor != NULL) { // Each time that cursor is not NULL, we have another occurrence of // target, so we add one to answer, and move cursor to the next // occurrence of the target. answer++; cursor = cursor->link; cursor = list_search(cursor, target); } return answer;
}
Bag operator +(const Bag& b1, const Bag& b2) { Bag answer; answer += b1; answer += b2; return answer; }
UAH
CPE 212
Bag 3 6
#ifndef LINK1_H #define LINK1_H #include <stdlib.h> // Provides size_t struct Node { typedef double Item; Item data; Node *link; // }; FUNCTIONS for the linked list toolkit size_t list_length(Node* head_ptr); void list_head_insert(Node*& head_ptr, const Node::Item& entry); void list_insert(Node* previous_ptr, const Node::Item& entry); Node* list_search(Node* head_ptr, const Node::Item& target); Node* list_locate(Node* head_ptr, size_t position); void list_head_remove(Node*& head_ptr); void list_remove(Node* previous_ptr); void list_clear(Node*& head_ptr); void list_copy(Node* source_ptr, Node*& head_ptr, Node*& tail_ptr); void list_piece(Node* start_ptr, Node* end_ptr, Node*& head_ptr, Node*& tail_ptr); #endif
UAH
CPE 212
#include <assert.h> #include <stdlib.h> #include "link1.h"
Bag 3 7
// Provides assert // Provides NULL and size_t
size_t list_length(Node* head_ptr) // Library facilities used: stdlib.h { Node *cursor; size_t answer; answer = 0; for (cursor = head_ptr; cursor != NULL; cursor = cursor->link) answer++; return answer; } void list_head_insert(Node*& head_ptr, const Node::Item& entry) { Node *insert_ptr; insert_ptr = new Node; insert_ptr->data = entry; insert_ptr->link = head_ptr; head_ptr = insert_ptr;
}
UAH
CPE 212
Bag 3 8
void list_insert(Node* previous_ptr, const Node::Item& entry) { Node *insert_ptr; insert_ptr = new Node; insert_ptr->data = entry; insert_ptr->link = previous_ptr->link; previous_ptr->link = insert_ptr;
} Node* list_search(Node* head_ptr, const Node::Item& target) { Node *cursor;
for (cursor = head_ptr; cursor != NULL; cursor = cursor->link) if (target == cursor->data) return cursor; return NULL; } Node* list_locate(Node* head_ptr, size_t position) { Node *cursor; size_t i; assert (0 < position); cursor = head_ptr; for (i = 1; (i < position) && (cursor != NULL); i++) cursor = cursor->link; return cursor; }
UAH
CPE 212
Bag 3 9
void list_head_remove(Node*& head_ptr) { Node *remove_ptr;
remove_ptr = head_ptr; head_ptr = head_ptr->link; delete remove_ptr;
}
void list_remove(Node* previous_ptr) { Node *remove_ptr; remove_ptr = previous_ptr->link; previous_ptr->link = remove_ptr->link; delete remove_ptr; }
void list_clear(Node*& head_ptr) // Library facilities used: stdlib.h { while (head_ptr != NULL) list_head_remove(head_ptr); }
UAH
CPE 212
Bag 3 10
void list_copy(Node* source_ptr, Node*& head_ptr, Node*& tail_ptr) // Library facilities used: stdlib.h { head_ptr = NULL; tail_ptr = NULL; // Handle the case of the empty list if (source_ptr == NULL) return; // Make the head node for the newly created list, and put data in it list_head_insert(head_ptr, source_ptr->data); tail_ptr = head_ptr; // Copy the rest of the nodes one at a time, adding at the tail of new list for (source_ptr = source_ptr->link; source_ptr != NULL; source_ptr = source_ptr->link) { list_insert(tail_ptr, source_ptr->data); tail_ptr = tail_ptr->link; } }
UAH
CPE 212
Bag 3 11
void list_piece(Node* start_ptr, Node* end_ptr, Node*& head_ptr, Node*& tail_ptr) // Library facilities used: stdlib.h { head_ptr = NULL; tail_ptr = NULL; // Handle the case of the empty list if (start_ptr == NULL) return;
// Make the head node for the newly created list, and put data in it list_head_insert(head_ptr, start_ptr->data); tail_ptr = head_ptr; if (start_ptr == end_ptr) return;
// Copy the rest of the nodes one at a time, adding at the tail of new list for (start_ptr = start_ptr->link; start_ptr != NULL; start_ptr = start_ptr->link) { list_insert(tail_ptr, start_ptr->data); tail_ptr = tail_ptr->link; if (start_ptr == end_ptr) return; } }
UAH
CPE 212
int main( ) { Bag ages;
Using The Bag
get_ages(ages); check_ages(ages); cout << "May your family live long and prosper." << endl; return EXIT_SUCCESS; } void get_ages(Bag& ages) { int user_input; // An age from the user's family
cout << "Type the ages in your family. "; cout << "Type a negative number when you are done:" << endl; cin >> user_input; while (user_input >= 0) { ages.insert(user_input); cin >> user_input; }
}
UAH
CPE 212
Using The Bag 2
void check_ages(Bag& ages) { int user_input; // An age from the user's family
cout << "Type those ages again. Press return after each age:" << endl; while (ages.size( ) > 0) { cin >> user_input; if (ages.occurrences(user_input) == 0) cout << "No, that age does not occur!" << endl; else { cout << "Yes, I've got that age and will remove it." << endl; ages.remove(user_input); } } }
UAH
CPE 212
Key Concepts
Implemented:
Default Constructor Copy Constructor Assignment Operator Destructor
Beware dereferencing the NULL pointer Verify NON-NULL pointer after a new operation