C++ Iterating through a linked list - c++

Question

So in my current program I am tasked to store a vector of branches. These branches contain a string name, and a pointer to a node.
These nodes store a book, which has an author name, a title, and the number of copies.
Overall, this should create the data structure of a linked list.
Currently I am attempting to write a program to print all the books within a branch.
After adding these books to the branch Alex.
Stan Moon
Bill Sun
Chris Ground
I attempt to print them all out using the printall() function. However, I simply get blank output. Is there something I am missing?
Thanks in advance!
#include "Library.h"
#include <vector>
#include <string>
#include <iostream>
using namespace std;
int total;
int index;
Library::Library()
{
}
struct Node //Has everything in it
{
string author;
string title;
int copies;
Node* next;
};
struct Branch // Stores just the branch, and a point to the node with information in it.
{
string b_name;
Node* next;
};
vector<Branch> lib;
void Library::start()
{
int choice;
cout << "Please select a choice." << endl;
cout << " " << endl;
cout << "1. Create a branch and insert its books" << endl;
cout << "2. Given an author name, a title and a branch name, CHECKOUT that book from the branch." << endl;
cout << "3. Given an author name, title and a branch name, RETURN that book to the branch." << endl;
cout << "4. Given an author name, title and branch name, FIND the number of copies of that book are available in that branch." << endl;
cout << "5. PRINT all books contained in a branch." << endl;
cout << "6. Exit the program." << endl;
cin >> choice;
if (choice == 1)
{
insert();
}
if (choice == 5)
{
printAll();
}
}
void Library::insert()
{
string br;
string auth;
string titl;
cout << "What is the name of the branch?" << endl;
cin >> br;
Branch *branch = new Branch();
branch->b_name = br;
lib.push_back(*branch);
if (total == 0)
{
cout << "What is the author and title of the book?" << endl;
cin >> auth >> titl;
Node *book = new Node();
book->author = auth;
book->title = titl;
book->copies++;
book->next = NULL;
branch->next = book;
total++;
}
do
{
cout << "What is the author and title of the book?" << endl;
cin >> auth >> titl;
Node *book = new Node();
book->author = auth;
book->title = titl;
book->copies++;
book->next = branch->next;
branch->next = book;
total++;
} while (auth != "NONE" && titl != "NONE");
start();
}
void Library::checkout()
{
string auth;
string titl;
string bran;
}
void Library::Return()
{
//TODO
}
void Library::find()
{
//TODO
}
void Library::printAll()
{
for (unsigned int i = 0; i < lib.size(); i++)
{
while (lib.at(i).next != NULL)
{
cout << "There are " << lib.at(i).next->copies << "of " << lib.at(i).next->title << "by " << lib.at(i).next->author << "in branch " << lib.at(i).b_name << endl;
lib.at(i).next = lib.at(i).next->next;
}
}
start();
}

Answer 1

I found some problems of your source code:
You should hold pointer in the lib vector, or it will be cloned when push_back
The insert function was wrongly implemented
You should use loop instead of recusive call, it maybe cause stack overflow
Check the modified version:
#include "Library.h"
#include <vector>
#include <string>
#include <iostream>
using namespace std;
int total;
int index;
Library::Library()
{
}
struct Node //Has everything in it
{
string author;
string title;
int copies;
Node* next;
};
struct Branch // Stores just the branch, and a point to the node with information in it.
{
string b_name;
Node* next;
};
vector<Branch*> lib;
void Library::start()
{
int choice = 0;
do
{
cout << "Please select a choice." << endl;
cout << " " << endl;
cout << "1. Create a branch and insert its books" << endl;
cout << "2. Given an author name, a title and a branch name, CHECKOUT that book from the branch." << endl;
cout << "3. Given an author name, title and a branch name, RETURN that book to the branch." << endl;
cout << "4. Given an author name, title and branch name, FIND the number of copies of that book are available in that branch." << endl;
cout << "5. PRINT all books contained in a branch." << endl;
cout << "6. Exit the program." << endl;
cin >> choice;
switch (choice)
{
case 1:
insert();
break;
case 5:
printAll();
break;
// TODO: other choises
}
} while (choice != 6);
}
void Library::insert()
{
string br;
string auth;
string titl;
cout << "What is the name of the branch?" << endl;
cin >> br;
Branch *branch = new Branch();
branch->b_name = br;
lib.push_back(branch);
Node* lastNode = nullptr;
do
{
cout << "What is the author and title of the book?" << endl;
cin >> auth >> titl;
Node *book = new Node();
book->author = auth;
book->title = titl;
book->copies++;
if (lastNode == nullptr) {
branch->next = book;
}
else {
lastNode->next = book;
}
lastNode = book;
} while (auth != "NONE" && titl != "NONE");
}
void Library::checkout()
{
string auth;
string titl;
string bran;
}
void Library::Return()
{
//TODO
}
void Library::find()
{
//TODO
}
void Library::printAll()
{
for (unsigned int i = 0; i < lib.size(); i++)
{
auto* branch = lib[i];
auto* node = branch->next;
while (node)
{
cout << "There are " <<
node->copies << " of " <<
node->title << " by " <<
node->author << " in branch " <<
branch->b_name << endl;
node = node->next;
}
}
}