CODEWITHSUNDEEP
cpointersmallocbinary-tree
Newuser1234567
Newuser1234567

Reputation: 23

Do I need to free in BinaryTree the root or the data?

I have a question... If I have a Binarytree like this:

typedef struct
{
   char* text;
   char* line;
   struct Node* left;
   struct Node* right;
}Node

and have a start function:

Node *start(Node* ptr)
{
if(ptr == NULL)
{
 ptr = (Node*)malloc(sizeof(Node));
    ptr->text = "some text";
    ptr->line = "another text";
    ptr->left = NULL;
    ptr->right = NULL;
}
return (ptr);
}

And a funtion to add left child in binarytree, if root is not empty and here I must give my text and line dynamic memory.

  Node* addNode(Node* ptr)
  {
    if(ptr != NULL)
    {
    Node* leftNode = (Node*)malloc(sizeof(zeiger));
    char* text = (char*) malloc(100*sizeof(char));
    char* line = (char*) malloc(100*sizeof(char));

    line = "some text 2";
    text = "another text";
    if(leftNode !=NULL)
    {
        leftNode->text = text;
        leftNode->line = line;
        leftNode->right = NULL;
        ptr->left = leftNode;
    }
    return leftNode;
}
return ptr;

}

Now the problem ist I want to free everything in tree so I have a a function like this to call himself if left or right or root is not NULL. So i saw some codes that I should free the root and not the datas.

void freeTree(Node* root)
{
  while(1)
  {
   if(root == NULL)
  {
  break;
}
else if (root->left != NULL)
{
  freeTree(root->left);
  root->left = NULL;
}
else if (root->right) {
        freeTree(root->right);
  root->right = NULL;
}
else
  {
  free(root);
  }
 }
}

Main.c

int main(int argc, char const *argv[]) {

Node* root = NULL;
root = start(root);
root = addNode(root);
freeTree(root);
return 0;
}

Upvotes: 0

Views: 284

Answers (1)

user2736738
user2736738

Reputation: 30926

You shouldn't free memory that you didn't malloc.

Here the first node's pointers are pointing to a string literal. You shouldn't call free() on them.

You should allocate memory in the initial node also and then try to copy that string literal. Now every node is similar.

Now you free the memory of each node. Which node to do first? The post order traversal would be the one. First the children, then the parent will should be freed, otherwise you will have memory leak.

void freeTree(Node *root){
   if( root ){
     freeTree(root->left);
     freeTree(root->right);
     free(root->text); // root->text was allocated calling malloc
     free(root->line); // same for root->line
     free(root);
   }
}

root->text was allocated calling malloc - You have to allocate dynamically to be able to call free on it. In your code the initial node's text is pointing to a string literal. You need to do it proper way as mentioned in answer - (allocate - and copy the string into newly allocated memory).

Upvotes: 2

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