Inserting node at rear end in a singly linked list

Question

I am coding on inserting a node at the end in a singly LinkedList. Program is executing without any errors but running an infinite loop after entering the very first number. I can't find the logical error I have committed in the code. Any help would be appreciable :).

Here is the code and what I've tried:

#include<bits/stdc++.h>
using namespace std;
struct node{
    int data;
    node* next;
};
node* head = NULL; // empty list
node* temp;
void insert(int x){
    temp = (node*)malloc(sizeof(node));
    temp -> data = x;
    temp -> next = NULL;
    if (head == NULL) head = temp; 
    node* temp1 = head;
    // traversing the list
    while(temp1 -> next != NULL){
    temp1 = temp1 -> next;
    }   
    temp1 -> next = temp;
}
void print(){
    node* iterator = head;
    while(iterator != NULL){
        cout << iterator -> data;
        iterator = iterator -> next;
    }
}
int main(){
    int n, x;
    cout << "how many numbers\n";
    cin >> n;
    for(int i = 0; i < n; i++){
        cout << "enter the value";
        cin >> x;
        insert(x);
        print();
    }
    return 0;
}

I expect the output to be a linked list but the o/p is an infinite number of first entered number/data ('x' in this case)

Answer 1

Well the logic of the insert function is clearly wrong

Lets step though it.

First you allocate the node and assign it to temp . Since this is C++ you should use new and you should use a constructor, but we'll let that pass.

Then since head equals NULL you set head to the temp .

Then you set temp1 to head , which because of the previous step means temp1 equals temp .

Then you loop to the last node pointed to by temp1 . In this case you're already at the last node so the loop isn't entered.

Then you set temp1->next to temp , but remember that temp1 equals temp , (see two steps previous), so now you've created a circular list. This explains your infinite loop.

I'm guessing that you meant to write this

if (head == NULL) { head = temp; return; }

or maybe this

if (head == NULL)
{
    head = temp; 
}
else
{
    ...
}