Question

I am trying to create a linked list where you can enter items into a list. I can enter the first item into the list but I am unable to add items after the first item without having the program crashing. Does anyone know whats wrong?

#include <string>
#include <iostream>

using namespace std;
struct node {
  string s;
  node *next;
};
  node *root;
  string ans;
  node *conductor;
void displayNodes() {
  conductor = root;
  while ( conductor != NULL ) {
  cout<< conductor->s << endl;
  conductor = conductor->next;
  }
}
void addNode(string str) {
    if (root == NULL) {
         root = new node; 
        root->next = NULL;
        root->s = str;
        conductor = root->next;
        return;
    }
    conductor->next = new node;
  conductor = conductor->next;
  conductor->next = NULL;
  conductor->s = str;
}
void deleteNode(string str) {
    while (conductor != NULL) {
        if (conductor->s == str) {
            conductor->next = conductor;
        } else {
            conductor = conductor->next;
        }
    }
}
int main() {
    while (true) {
        system("cls");
        cout << "Enter a string: ";
        cin >> ans;
        addNode(ans);
        system("cls");
        displayNodes();
        system("pause");
    }
  system("pause");
  return EXIT_SUCCESS;
}

Answer 1

Because the first time you set

conductor = root->next;

which is now NULL, and at the next attempt

conductor->next = new node;

which is undefined behavior.

What you should do is set

conductor = root;

at the first iteration. conductor should point to the last created node, not to NULL.