Binary Tree

[noname1810]

Hello, everybody!

I'm writing a code, which should be able to insert a node to a binary tree where specified. Commands are being loaded from a .txt file.

The contents of the .txt file are the following:

1
L 1 2
R 1 3
L 2 6
R 2 4
L 3 5
R 3 7
F

first line stands for the root data
L stands for the left node
R stand for the right node
first digit stands for the data of a node to which a child must be added
second digit stands for the data of the child which is about to be inserted

That means that the command L 2 6 means "add a child with data '6' to a node with data '2'.

Here is the code i've written so far:

#include <iostream>
#include <fstream>
using namespace std;

struct node{
       int data;
       node *left;
       node *right;
};

node *tree=NULL;
void add_node(node *tree, char how, int where, int what);
node *search(node *tree, int where);
node *search(node *some, int somewhere);
void print_inorder(node *tree);

int main(){
    int start;
    char how;
    int where, what;
    
    ifstream fin("test.txt");
    fin>>start;
    tree = new node;
    tree->left=tree->right=NULL;
    tree->data=start;
    //cout<<tree->data;
    
    do {
        fin>>how>>where>>what;
        add_node(tree, how, where, what);
        } while(how!='F');
    
    print_inorder(tree);

system("pause");
return 0;

}

void add_node(node *tree, char how, int where, int what){
     node *p=tree;
     p=search(p, where);
     
        if(p->data==where) {
           if (how=='L'){
           p->left=new node;
           p->left->data=what;
           p->left->left=p->left->right=NULL;
           }
     
           if (how=='R'){
           p->right=new node;
           p->right->data=what;
           p->right->left=p->right->right=NULL;
           }
        }
        
     return;
}

node *search(node *some, int somewhere){
     if(some->data==somewhere) return some;
     else{
          search(some->left, somewhere);
          search(some->right, somewhere);
          }
}   
    

void print_inorder(node *tree) {
    if (tree!=NULL) {
        print_inorder(tree->left);  
        cout<<tree->data<<endl;     
        print_inorder(tree->right); 
    }
}

The problem is that OS stops the execution with an error and the debugger says: An Access Violation (Segmentation fault) raised in your program. I would appreciate some help, thank you in advance.

P.S. When file contains only 3 commands, like

1
L 1 2
R 1 3

everything goes smooth.

[ne555]

node *search(node *some, int somewhere){
     if(some->data==somewhere) return some;
     else{
          search(some->left, somewhere);
          search(some->right, somewhere);
          }
}

The node will not be in all the paths. You need to stop the recursion when you reach a leaf

[noname1810]

Thank you. Could you please help me with modifying this part of code.

P.S. Doesn't this line:

if(some->data==somewhere) return some;

stop the recursion, as you say?

[ne555]

That will only stop if you found it.
But what if you reach a leaf that doesn't have your number? You will launch the recursion to its sons (that are both NULL), so you will dereference a null pointer -> crash.

By the way, you don't have a return statement on the else part so your function just works for the root.