Adding Data to Linked List after Sorting - c++

Question

I am trying to read a text file,sort it each user with respect to their number in text file then add it to the linked list.then display it again respect to user number of each node in descending order.also i am trying to add functions to edit like deleting or updating the content.
txt file is like
John Doe ; 10
Sally Tully ; 5
James Watson ; 12
what i have achieved is this:
list.h:
#include<string>
#ifndef LIST_H
#define LIST_H
class list{
private:
struct node{
std::string data;
node* next;
};
typedef struct node* nodePtr;
nodePtr head;
nodePtr curr;
nodePtr temp;
public:
list();
void AddNode(std::string addData);
void DeleteNode(std::string delData);
void PrintList();
};
#endif
list.cpp
#include <cstdlib>
#include <iostream>
#include "list.h"
using namespace std;
list::list(){ //constructor
head = NULL;
curr= NULL;
temp=NULL;
}
void list::AddNode(string addData){
nodePtr n = new node; //nodePtr is node*
n->next=NULL; //find node n is pointing to, access its next element make it point to null
n->data= addData;
if(head != NULL) { // if we have at least 1 element in the list .
curr = head; // take the current pointer we are working with and make it same with head pointer pointing to.(current= front of list)
while(curr->next !=NULL){ // are we at the end of the list.
curr = curr->next;//we are not end of the list.curr pointer points next node.
}
curr->next = n;
}else{ //if we dont have at least 1 element in the list.
head =n;
}
}
void list::DeleteNode(string delData){
nodePtr delPtr = NULL;
temp = head;
curr = head;
while(curr != NULL && curr->data != delData){ // look for data user wants to delete
temp = curr;
curr = curr->next;
}
if(curr == NULL){ // we cant find we are looking for.
cout << delData << "not in list"<<endl;
delete delPtr;
}else{ // we found it
delPtr = curr;
curr = curr->next; // with those 2 lines we are patching the hole in the list.
temp->next = curr;
if(delPtr == head){
head = head->next;
temp = NULL;
}
delete delPtr;
cout<<delData<<"deleted"<<endl;
}
}
void list::PrintList(){
curr = head;
while(curr !=NULL){
cout<<curr->data<<endl;
curr = curr->next;
}
}
int main(){
list mylist;
mylist.AddNode("hello");
mylist.AddNode("how u doin");
mylist.AddNode("good");
mylist.PrintList();
return 0;
}
after reading the txt file should i put them into a vector(or directly to list) then sort then put to linked list ? i guess its wrong i should put them directly then sort before printing on screen. also i dont have any idea how to do updating node by user input function.
update:
I achieved adding content to linked list from txt file.
string file;
ifstream filein;
cout << "Enter file name:"<<endl;
cin >> file;
filein.open(file);
for(;filein.fail();)
{
cout << "Cannot open the file"<<endl;
cout << "Enter file name:"<<endl;
cin >> file;
filein.open(file);
}
string cline;
string cname;
string csurname;
int money;
string smoney;
string lastdata;
char delimiter=';';
while (std::getline(filein, cline)){
std::istringstream iss(cline);
while(iss >> cname >> csurname >> delimiter >> money){
ostringstream temp; // int to string
temp<<money;
smoney=temp.str();
lastdata = cname+" "+csurname+" "+smoney;
mylist.AddNode(lastdata);
}
}
mylist.PrintList();
now it adds like
john doe 10
sally tully 5
the problem is how im gonna reach this 10 and sort them while printing on screen

Answer 1

One way o solve the problem is to create two kinds of methods, one that deals with the comparison and other one that sort the linked list.
The below method deals with comparison. In this case it is comparing the length of the string, but it could be anything.
bool list::IsGreater(nodePtr a, nodePtr b)
{
if (a->data.length() > b->data.length())
return true;
return false;
}
The second method sorts the linked list. Even if there is a sort method, the easiest way is to keep the list sorted during the method AddNode.
void list::SortList() {
for (nodePtr i = head; i != NULL; i = i->next) {
nodePtr prev = NULL;
for (nodePtr j = head; j != NULL && j->next != NULL; j = j->next) {
if (IsGreater(j, j->next)) {
if (prev)
prev->next = j->next;
else
head = j->next;
nodePtr tmp = j->next;
j->next = j->next->next;
tmp->next = j;
j = tmp;
}
if (prev == NULL)
prev = head;
else
prev = j;
}
prev = i;
}
}