通过从几乎工作的文本文件中读取来将节点附加到链表
Appending nodes to linked list by reading from text file almost working
大家好！我有一个程序，它有一个链表，其中每个节点都有一个字符串名称和一个用于各自名称的 ID 的 int，追加、前置、插入后、删除等函数工作正常，但我需要实现以便它从一个文本文件中读取，示例：
使用此代码
case 9:
{
file.open("Attendance.txt");
while (!file.eof())
{
file>>node->attendeename>>node->key;
attendance.appendAttendee(node);
}
cout << "imported\n";
}
break;
当我尝试 运行 该选项时，它仅将文本文件的最后一行附加为节点，console:
这是完整的程序代码，程序的其余部分是与朋友和网络资源合作完成的，我不声称这是我自己的
#include <iostream>
#include <iomanip>
#include <bits/stdc++.h>
#include <sstream>
#include <fstream>
using namespace std;
//linked list node
class Node {
public:
int key;
string attendeename;
Node* next;
};
class LinkedList {
public:
Node * head;
//default constructor
LinkedList() {
head = NULL;
}
//Have head point to the node
LinkedList(Node * n) {
head = n;
}
// Checks if node exists using key value
Node * keyAlreadyExists(int k) {
Node * check = NULL;
Node * ptr = head;
while (ptr != NULL) {
if (ptr -> key == k) //checks if k already exists as a key
{
check = ptr;
}
ptr = ptr -> next;
}
return check;
}
//Append a node to the end of the list
void appendAttendee(Node * n) {
if (keyAlreadyExists(n -> key) != NULL) //first checks if a node already exists with n -> key
{
cout << "----- Node Already exists with key value : " << n -> key << ". Append another node with different Key value -----" << endl << endl;
}
else
{
if (head == NULL) //checks if list is empty
{
head = n; //the node becomes the head of the list
cout << "----- Node Has Been Appended -----" << endl << endl;
}
else
{
Node * ptr = head;
while (ptr -> next != NULL) //traverses to the end of the list
{
ptr = ptr -> next;
}
ptr -> next = n; // the current last node will now point to the passed node
cout << "----- Node Has Been Appended -----" << endl << endl;
}
}
}
// add node to the start of the list
void prependAttendee(Node * n) {
if (keyAlreadyExists(n -> key) != NULL) //first checks if a node already exists with n -> key
{
cout << "----- A Node Already exists with key value : " << n -> key << ". Append another node with different Key value -----" << endl;
}
else
{
n -> next = head; //makes node n point to the address of head
head = n;
cout << "----- Node Has Been Prepended -----" << endl << endl;
}
}
// insert a node after a specific node in the list
void insertAttendee(int k, Node * n) {
if (head == NULL) //checks if their is already a node in the list
{
cout << "----- Attendance list is still empty, can't add after key-----" << endl << endl;
} else {
Node * ptr = keyAlreadyExists(k); //checks if the int k that is passed does exist inside the list
if (ptr == NULL)
{
cout << "----- No node exists with key value: " << k << " -----" << endl << endl;
}
else
{
if (keyAlreadyExists(n -> key) != NULL) //checks if the key in the new node to be added, already exists in the list
{
cout << "-----A Node Already exists with key value : " << n -> key << ". Append another node with different Key value -----" << endl << endl;
}
else
{
n -> next = ptr -> next; //makes the newly added node point to the node that the previous node was pointing to
ptr -> next = n; //links the node that has the chosen key point to the new node
cout << "----- Node Has Been Inserted -----" << endl << endl;
}
}
}
}
// Delete a node that has the key int k
void deleteAttendee(int k) {
if (head == NULL) //checks if their is already a node in the list
{
cout << "----- Attendance list already empty. Cannot delete anymore -----" << endl << endl;
} else if (head != NULL) {
//checks if int k belongs to the key of head node
if (head -> key == k) {
head = head -> next; //makes head pointer point to the node after the head node
cout << "----- Attendee with key ID " << k << " deleted -----" << endl << endl;
} else {
Node * temp = NULL;
Node * prevptr = head;
Node * currentptr = head -> next;
while (currentptr != NULL) {
//checks if the key of currenptr is int k
if (currentptr -> key == k) {
temp = currentptr;
//gets rid of the node of currentpr
currentptr = NULL;
} else {
//moves on to the next node
prevptr = prevptr -> next;
currentptr = currentptr -> next;
}
}
//checks if a node has been deleted
if (temp != NULL) {
//makes the previous pointer point to the node after the deleted node
prevptr -> next = temp -> next;
cout << "----- Attendee with key ID " << k << " deleted -----" << endl << endl;
} else {
cout << "----- Attendee doesn't exist with key ID " << k << " -----" << endl << endl;
}
}
}
}
// update the info of a node with a specific key
void updateAttendeeInfo(int k, string name) {
//checks if a node with key int k exists
Node * ptr = keyAlreadyExists(k);
if (ptr != NULL) {
//updates the data of the node
ptr -> attendeename = name;
cout << "----- Information Updated Successfully -----" << endl << endl;
}
//output if no node contains the key int k
else {
cout << "----- No Attendee has this key ID " << k << " -----" << endl << endl;
}
}
// function to print the entire linked list
void printAttendanceList() {
//checks if the linked list contains any nodes
if (head == NULL)
{
cout << "----- No attendees recorded in list -----";
}
else
{
cout << endl << "----- List of Attendees -----" << endl;
Node * temp = head;
//to print the key and data of every node in the list
while (temp != NULL)
{
cout << "Name: " << temp -> attendeename << setw(7) << "ID: " << temp -> key;
temp = temp -> next;
cout << endl;
}
}
cout << endl << endl;
}
//function to output the entire linked list to text file
void backupAttendanceList()
{
ofstream file("Attendance.txt");
Node * temp = head;
//to print the key and data of every node in the list
while (temp != NULL)
{
file << temp -> attendeename << setw(7) << temp -> key;
temp = temp -> next;
file << endl;
}
cout << "----- Attendance list backed up successfully -----" << endl << endl;
}
} ;
int main() {
LinkedList attendance;
int choice, id, nodekey;
fstream file;
string name;
//menu screen
do {
//new node;
Node * node = new Node();
cout << "Welcome to the event! Please select option to do from the registration menu:" << endl << endl;
cout << "1 - Add attendance" << endl;
cout << "2 - Insert attendance on front of list" << endl;
cout << "3 - Insert attendance after certain key ID" << endl;
cout << "4 - Delete attendance by key ID" << endl;
cout << "5 - Update attendance details by key ID" << endl;
cout << "6 - Print list of attendees" << endl;
cout << "7 - Clear screen" << endl;
cout << "8 - Backup to text file" << endl;
cout << "9 - Import from text file" << endl;
cout << "10 - Exit Program" << endl << endl;
cout << "Your Choice: "; cin >> choice;
cout << endl;
switch (choice) {
//add attendance
case 1:
cout << "Add your attendance details. Please enter the following:" << endl
<< "Key Data: ";
cin >> id;
cin.ignore();
cout << "Name: ";
getline (cin,name);
cout << endl;
node -> key = id;
node -> attendeename = name;
attendance.appendAttendee(node);
break;
//insert attendance to top
case 2:
cout << "Insert attendance from top of list. Please enter the following:" << endl
<< "Key Data: ";
cin >> id;
cin.ignore();
cout << "Name: ";
getline (cin,name);
cout << endl;
node -> key = id;
node -> attendeename = name;
attendance.prependAttendee(node);
break;
//insert attendance after a certain node
case 3:
cout << "Insert attendance. After which key ID you want to be inserted? " << endl
<< "Key ID of attendee you want to insert after: ";
cin >> nodekey;
cout << "Add your attendance details. Please enter the following:" << endl
<< "Key Data: ";
cin >> id;
cin.ignore();
cout << "Name: ";
getline (cin,name);
cout << endl;
node -> key = id;
node-> attendeename = name;
attendance.insertAttendee(nodekey, node);
break;
//deletion of attendance
case 4:
cout << "Delete attendance. Please enter key ID to be deleted: ";
cin >> nodekey;
cout << endl;
attendance.deleteAttendee(nodekey);
break;
//update attendance
case 5:
cout << "Update existing attendance. Please enter the following:" << endl
<< "Key Data: ";
cin >> id;
cin.ignore();
cout << "Updated Name: ";
getline (cin,name);
cout << endl;
attendance.updateAttendeeInfo(id, name);
break;
//print recorded list
case 6:
attendance.printAttendanceList();
break;
//clears console screen
case 7:
system("cls");
break;
//creates txt file
case 8:
attendance.backupAttendanceList();
break;
case 9:
{
file.open("Attendance.txt");
while (!file.eof())
{
file>>node->attendeename>>node->key;
attendance.appendAttendee(node);
}
cout << "imported\n";
}
break;
//exits the program
case 10:
cout<< "Now closing program" <<endl;
exit(1);
default:
cout << "Invalid Option Number Entered, Enter Again:" << endl;
}
} while (choice != 10);
return 0;
}
主要问题是您重复追加同一个节点。
Node* node = new Node();
...
while (!file.eof())
{
file>>node->attendeename>>node->key;
attendance.appendAttendee(node);
}
您的代码应该为文件中的每个项目创建一个新节点，如下所示
while (!file.eof())
{
Node* node = new Node();
file>>node->attendeename>>node->key;
attendance.appendAttendee(node);
}
我不认为我说这段代码中可能有多个问题（我可以立即看到另一个）是不合时宜的。但我会留给你去找出那些。
大家好！我有一个程序，它有一个链表，其中每个节点都有一个字符串名称和一个用于各自名称的 ID 的 int，追加、前置、插入后、删除等函数工作正常，但我需要实现以便它从一个文本文件中读取，示例：
使用此代码
case 9:
{
file.open("Attendance.txt");
while (!file.eof())
{
file>>node->attendeename>>node->key;
attendance.appendAttendee(node);
}
cout << "imported\n";
}
break;
当我尝试 运行 该选项时，它仅将文本文件的最后一行附加为节点，console:
这是完整的程序代码，程序的其余部分是与朋友和网络资源合作完成的，我不声称这是我自己的
#include <iostream>
#include <iomanip>
#include <bits/stdc++.h>
#include <sstream>
#include <fstream>
using namespace std;
//linked list node
class Node {
public:
int key;
string attendeename;
Node* next;
};
class LinkedList {
public:
Node * head;
//default constructor
LinkedList() {
head = NULL;
}
//Have head point to the node
LinkedList(Node * n) {
head = n;
}
// Checks if node exists using key value
Node * keyAlreadyExists(int k) {
Node * check = NULL;
Node * ptr = head;
while (ptr != NULL) {
if (ptr -> key == k) //checks if k already exists as a key
{
check = ptr;
}
ptr = ptr -> next;
}
return check;
}
//Append a node to the end of the list
void appendAttendee(Node * n) {
if (keyAlreadyExists(n -> key) != NULL) //first checks if a node already exists with n -> key
{
cout << "----- Node Already exists with key value : " << n -> key << ". Append another node with different Key value -----" << endl << endl;
}
else
{
if (head == NULL) //checks if list is empty
{
head = n; //the node becomes the head of the list
cout << "----- Node Has Been Appended -----" << endl << endl;
}
else
{
Node * ptr = head;
while (ptr -> next != NULL) //traverses to the end of the list
{
ptr = ptr -> next;
}
ptr -> next = n; // the current last node will now point to the passed node
cout << "----- Node Has Been Appended -----" << endl << endl;
}
}
}
// add node to the start of the list
void prependAttendee(Node * n) {
if (keyAlreadyExists(n -> key) != NULL) //first checks if a node already exists with n -> key
{
cout << "----- A Node Already exists with key value : " << n -> key << ". Append another node with different Key value -----" << endl;
}
else
{
n -> next = head; //makes node n point to the address of head
head = n;
cout << "----- Node Has Been Prepended -----" << endl << endl;
}
}
// insert a node after a specific node in the list
void insertAttendee(int k, Node * n) {
if (head == NULL) //checks if their is already a node in the list
{
cout << "----- Attendance list is still empty, can't add after key-----" << endl << endl;
} else {
Node * ptr = keyAlreadyExists(k); //checks if the int k that is passed does exist inside the list
if (ptr == NULL)
{
cout << "----- No node exists with key value: " << k << " -----" << endl << endl;
}
else
{
if (keyAlreadyExists(n -> key) != NULL) //checks if the key in the new node to be added, already exists in the list
{
cout << "-----A Node Already exists with key value : " << n -> key << ". Append another node with different Key value -----" << endl << endl;
}
else
{
n -> next = ptr -> next; //makes the newly added node point to the node that the previous node was pointing to
ptr -> next = n; //links the node that has the chosen key point to the new node
cout << "----- Node Has Been Inserted -----" << endl << endl;
}
}
}
}
// Delete a node that has the key int k
void deleteAttendee(int k) {
if (head == NULL) //checks if their is already a node in the list
{
cout << "----- Attendance list already empty. Cannot delete anymore -----" << endl << endl;
} else if (head != NULL) {
//checks if int k belongs to the key of head node
if (head -> key == k) {
head = head -> next; //makes head pointer point to the node after the head node
cout << "----- Attendee with key ID " << k << " deleted -----" << endl << endl;
} else {
Node * temp = NULL;
Node * prevptr = head;
Node * currentptr = head -> next;
while (currentptr != NULL) {
//checks if the key of currenptr is int k
if (currentptr -> key == k) {
temp = currentptr;
//gets rid of the node of currentpr
currentptr = NULL;
} else {
//moves on to the next node
prevptr = prevptr -> next;
currentptr = currentptr -> next;
}
}
//checks if a node has been deleted
if (temp != NULL) {
//makes the previous pointer point to the node after the deleted node
prevptr -> next = temp -> next;
cout << "----- Attendee with key ID " << k << " deleted -----" << endl << endl;
} else {
cout << "----- Attendee doesn't exist with key ID " << k << " -----" << endl << endl;
}
}
}
}
// update the info of a node with a specific key
void updateAttendeeInfo(int k, string name) {
//checks if a node with key int k exists
Node * ptr = keyAlreadyExists(k);
if (ptr != NULL) {
//updates the data of the node
ptr -> attendeename = name;
cout << "----- Information Updated Successfully -----" << endl << endl;
}
//output if no node contains the key int k
else {
cout << "----- No Attendee has this key ID " << k << " -----" << endl << endl;
}
}
// function to print the entire linked list
void printAttendanceList() {
//checks if the linked list contains any nodes
if (head == NULL)
{
cout << "----- No attendees recorded in list -----";
}
else
{
cout << endl << "----- List of Attendees -----" << endl;
Node * temp = head;
//to print the key and data of every node in the list
while (temp != NULL)
{
cout << "Name: " << temp -> attendeename << setw(7) << "ID: " << temp -> key;
temp = temp -> next;
cout << endl;
}
}
cout << endl << endl;
}
//function to output the entire linked list to text file
void backupAttendanceList()
{
ofstream file("Attendance.txt");
Node * temp = head;
//to print the key and data of every node in the list
while (temp != NULL)
{
file << temp -> attendeename << setw(7) << temp -> key;
temp = temp -> next;
file << endl;
}
cout << "----- Attendance list backed up successfully -----" << endl << endl;
}
} ;
int main() {
LinkedList attendance;
int choice, id, nodekey;
fstream file;
string name;
//menu screen
do {
//new node;
Node * node = new Node();
cout << "Welcome to the event! Please select option to do from the registration menu:" << endl << endl;
cout << "1 - Add attendance" << endl;
cout << "2 - Insert attendance on front of list" << endl;
cout << "3 - Insert attendance after certain key ID" << endl;
cout << "4 - Delete attendance by key ID" << endl;
cout << "5 - Update attendance details by key ID" << endl;
cout << "6 - Print list of attendees" << endl;
cout << "7 - Clear screen" << endl;
cout << "8 - Backup to text file" << endl;
cout << "9 - Import from text file" << endl;
cout << "10 - Exit Program" << endl << endl;
cout << "Your Choice: "; cin >> choice;
cout << endl;
switch (choice) {
//add attendance
case 1:
cout << "Add your attendance details. Please enter the following:" << endl
<< "Key Data: ";
cin >> id;
cin.ignore();
cout << "Name: ";
getline (cin,name);
cout << endl;
node -> key = id;
node -> attendeename = name;
attendance.appendAttendee(node);
break;
//insert attendance to top
case 2:
cout << "Insert attendance from top of list. Please enter the following:" << endl
<< "Key Data: ";
cin >> id;
cin.ignore();
cout << "Name: ";
getline (cin,name);
cout << endl;
node -> key = id;
node -> attendeename = name;
attendance.prependAttendee(node);
break;
//insert attendance after a certain node
case 3:
cout << "Insert attendance. After which key ID you want to be inserted? " << endl
<< "Key ID of attendee you want to insert after: ";
cin >> nodekey;
cout << "Add your attendance details. Please enter the following:" << endl
<< "Key Data: ";
cin >> id;
cin.ignore();
cout << "Name: ";
getline (cin,name);
cout << endl;
node -> key = id;
node-> attendeename = name;
attendance.insertAttendee(nodekey, node);
break;
//deletion of attendance
case 4:
cout << "Delete attendance. Please enter key ID to be deleted: ";
cin >> nodekey;
cout << endl;
attendance.deleteAttendee(nodekey);
break;
//update attendance
case 5:
cout << "Update existing attendance. Please enter the following:" << endl
<< "Key Data: ";
cin >> id;
cin.ignore();
cout << "Updated Name: ";
getline (cin,name);
cout << endl;
attendance.updateAttendeeInfo(id, name);
break;
//print recorded list
case 6:
attendance.printAttendanceList();
break;
//clears console screen
case 7:
system("cls");
break;
//creates txt file
case 8:
attendance.backupAttendanceList();
break;
case 9:
{
file.open("Attendance.txt");
while (!file.eof())
{
file>>node->attendeename>>node->key;
attendance.appendAttendee(node);
}
cout << "imported\n";
}
break;
//exits the program
case 10:
cout<< "Now closing program" <<endl;
exit(1);
default:
cout << "Invalid Option Number Entered, Enter Again:" << endl;
}
} while (choice != 10);
return 0;
}
主要问题是您重复追加同一个节点。
Node* node = new Node();
...
while (!file.eof())
{
file>>node->attendeename>>node->key;
attendance.appendAttendee(node);
}
您的代码应该为文件中的每个项目创建一个新节点，如下所示
while (!file.eof())
{
Node* node = new Node();
file>>node->attendeename>>node->key;
attendance.appendAttendee(node);
}
我不认为我说这段代码中可能有多个问题（我可以立即看到另一个）是不合时宜的。但我会留给你去找出那些。