如何从右到左在C中的树中插入节点？

Question

Now, I understand that code below works only for root and its children, but I don't know how to expand it. Every node must have children before passing on "grandchildren". Thank you.

void insert_node(IndexTree **root, Node *node) {
    IndexTree *temp = (IndexTree*)malloc(sizeof(IndexTree));
    memcpy(&temp->value.cs, node, sizeof(Node));
    temp->left = NULL;
    temp->right = NULL;
    temp->tip=1;

if ((*root) == NULL) {
    *root = temp;
    (*root)->left = NULL;
    (*root)->right = NULL;
}
else {
    while (1) {
        if ((*root)->right == NULL) {
            (*root)->right = temp;
            break;
        }
        else if ((*root)->left == NULL) {
            (*root)->left = temp;
            break;
        }
    }
}

Answer 1

Use recursive functions.

Trees are recursive data types ( https://en.wikipedia.org/wiki/Recursive_data_type ). In them, every node is the root of its own tree. Trying to work with them using nested if s and while s is simply going to limit you on the depth of the tree.

Consider the following function: void print_tree(IndexTree* root) . An implementation that goes over all values of the trees does the following:

void print_tree(IndexTree* root)
{
      if (root == NULL) return; // do NOT try to display a non-existent tree

      print_tree(root->right);
      printf("%d\n", root->tip);
      print_tree(root->left);
}

The function calls itself, which is a perfectly legal move, in order to ensure that you can parse an (almost) arbitrarily deep tree. Beware, however, of infinite recursion! If your tree has cycles (and is therefore not a tree), or if you forget to include an exit condition, you will get an error called... a Stack Overflow! Your program will effectively try to add infinite function calls on the stack, which your OS will almost certainly dislike.

As for inserting, the solution itself is similar to that of printing the tree:

void insert_value(IndexTree* root, int v)
{
    if (v > root->tip) {
        if (root->right != NULL) {
            insert_value(root->right, v);
        } else {
            // create node at root->right
        }
    } else {
        // same as above except with root->left
    }
}

Answer 2

It may be an interesting programming question to create a Complete Binary Tree using linked representation. Here Linked mean a non-array representation where left and right pointers(or references) are used to refer left and right children respectively. How to write an insert function that always adds a new node in the last level and at the leftmost available position? To create a linked complete binary tree, we need to keep track of the nodes in a level order fashion such that the next node to be inserted lies in the leftmost position. A queue data structure can be used to keep track of the inserted nodes.
Following are steps to insert a new node in Complete Binary Tree. (Right sckewed)
1. If the tree is empty, initialize the root with new node.

2. Else, get the front node of the queue.

……. if the right child of this front node doesn't exist, set the right child as the new node. //as per your case
…….else If the left child of this front node doesn't exist, set the left child as the new node.

3. If the front node has both the left child and right child, Dequeue() it.

4. Enqueue() the new node .