C++ 双向链表按字母顺序和值添加节点

Question

My task is a create doubly linked list and sort them according to their data, if new written node's data is equal to the one of the nodes' data in my doubly linked list, i should sort them in a alphabetical order but I am stuck in the function strcmp(temp->name, newnode->name) , For example, I am trying to check if these values entered in order

1. Christian 250
2. Tom 200
3. Alex 250

My sorted doubly linked list give the output as

1. Alex 250
2. Christian 250
3. Tom 200

Here is example of my code

   struct node {
    int data;
    string name;
    node* left;
    node* right;

    node(int i = 0, string s = "", node* l = nullptr, node* r = nullptr) : data(i), name(s), left(l), right(r) {}
};

struct node* head = NULL;
struct node* tail = NULL;

at the top of the program

void insert(int newdata, string name)  // Used for insertion at the end of the linked list and make 
{                                      // the connection for each of the node
    node* newnode = new node();
    node* nodehead = head;
    newnode->data = newdata;
    newnode->name = name;
    newnode->right = NULL;

    if( head == NULL)
    {
        newnode -> left = NULL;
        head = tail = newnode;
    }
    else 
    {
        while (nodehead->right != NULL)
        {
            nodehead = nodehead->right;     
        }
            nodehead->right = newnode; // make the connection for each of them
            newnode->left = nodehead;
            tail = newnode; // and newly created node is our tail

            sorting(newnode); // then go the function to sort them 
    }
   
    cout << "New node is added " << newnode->name << " " << newnode->data << endl;
}

then sort them based on their comparison of their data and if they are equal i should check based on their alphabetical order

 void sorting( node *  &newnode) // ı call sorting function in the insertion function
    {
        node* temp = head;
        node* temp2 = newnode;
    
        int numtemp;
    
        while (temp != nullptr)
        {
            node* temp2 = temp->right;
            while (temp2 != nullptr)
            {       
                if (temp2->data > temp->data) // comparison of their data if newnode's data is larger 
                {
                    string strtemp = "";
                    numtemp = temp->data; // Change their number
                    temp->data = temp2->data;
                    temp2->data = numtemp;
    
                    strtemp = temp->name; // Change their name
                    temp->name = temp2->name;
                    temp2->name = strtemp;
                }
                else if (temp2->data = temp->data) // if newly data is equal to linked list data
                {
                    int ret;
                    ret =  strcmp(temp2->name, temp->name); // i tried to check their string comparison but it did not work
                }
                temp2 = temp2->right;
            }
            temp = temp->right;
        }        
    }

Answer 1

I'd recommend that you define a comparison on the node itself, and use that in sorting. Keep in mind that if you are comparing through pointers, you'll need to dereference (compare the nodes, not the pointers).

The standard library already has a way to do comparison based on multiple terms. https://en.cppreference.com/w/cpp/utility/tuple/tie

using std::tie ensures that you meet https://en.wikipedia.org/wiki/Weak_ordering#Strict_weak_orderings

I am, of course, assuming that std::string's comparison meets your need for alphabetical. If that's not the case, this may need a minor tweek.

#include <string>
#include <iostream>

struct node {
    int data;
    std::string name;
    node* left;
    node* right;

    node(int i = 0, std::string s = "", node* l = nullptr, node* r = nullptr) 
        : data(i), name(s), left(l), right(r) 
    {}

    bool operator< (const node & rhs) {
        return std::tie(data, name) < std::tie(rhs.data, rhs.name);
    }
};

int main(){
    // simplistic demo
    node a { 21, "green" };
    node b { 21, "yellow" };
    node * p1 = &a;
    node * p2 = &b;
    bool less = (*p1) < (*p2);
    if (p1->data == p2->data) {
        if (*p1 < *p2) {
            std::cout << p1->name << " < " << p2->name << std::endl;
        } else {
            std::cout << p1->name << " >= " << p2->name << std::endl;
        }
    }
}

Answer 2

ı basically add in the else if part if the values are same and change names but appreantly it changes whole list of numbers

void sorting( node *  &newnode) 
{

    node* temp = head;
    node* temp2 = newnode;

    int numtemp;


    while (temp != nullptr)
    {
        node* temp2 = temp->right;
        while (temp2 != nullptr)
        {

            if (temp2->data > temp->data)
            {
                string strtemp = "";
                numtemp = temp->data; // num change
                temp->data = temp2->data;
                temp2->data = numtemp;

                strtemp = temp->name; // name change
                temp->name = temp2->name;
                temp2->name = strtemp;

            }
            else if (temp2->data == temp->data) // here is the change 
            {
               if(temp2->name > temp->name ) // make comparison but im not sure wheteris logical or not 
               {
                   string strtemp = "";
                   strtemp = temp->name; // name change
                   temp->name = temp2->name;
                   temp2->name = strtemp;
               
               }
                
                 
                
            }

            temp2 = temp2->right;
        }

        temp = temp->right;
    }

   

}

Answer 3

Your comparison operator is bad:

              if(temp2->name < temp->name ) // make comparison but im not sure wheteris logical or not 
               {
                   string strtemp = "";
                   strtemp = temp->name; // name change
                   temp->name = temp2->name;
                   temp2->name = strtemp;
               
               }

Should be < .