Compiler error recursion linked list

Question

int insert(node* head) {
    if (head == NULL) {
        node* temp = new node;
        if (head == NULL) {
            cout << "Error";
            return 0;
        }
        temp->data = 20;
        temp->next = NULL;
    } else {
        temp->next = insert(temp->next);
    }
    return (temp);
}

I am trying to add node recursively but I got the error temp was not declared. I do not understand why I am getting this error. When I always define temp like this node* temp = new node; but now I got an error.

It doesn't really make sense for insert to return something. Besides, your return type is int but you're returning a node* in return temp. Just make the return type void. — David G
– David G, Commented Nov 20, 2014 at 4:07
@0x499602D2, std::list's insert returns an iterator to the inserted element. — Qaz
– Qaz, Commented Nov 20, 2014 at 4:14

Jonathan Potter · Accepted Answer · 2014-11-20 03:58:39Z

1

Local variables are only visible inside the scope they're declared in, and you're declaring temp inside your first if statement. You need to move the definition outside the if clause:

int insert(node* head)
{
     node* temp=new node; // <- move to here
     if(head==NULL)
     {
          ...
     }
     else
     {
          ...
     }
     return temp;
}

answered Nov 20, 2014 at 3:58

Jonathan Potter

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Comments

Shriraj · Accepted Answer · 2014-11-20 05:20:44Z

0

There seems to be multiple issues with your code:

int insert(node* head) { if (head == NULL) { node* temp = new node; // Newly created node will not be used at all if (head == NULL) { // as head is NULL it will return 0 cout << "Error"; return 0; } temp->data = 20; // Code unreachable temp->next = NULL; } else { temp->next = insert(temp->next); // Here you will again get an error for temp not declared } return (temp); }

answered Nov 20, 2014 at 5:20

Shriraj

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