如何在非变体二叉树中搜索给定节点的父节点？

Question

I have the code for searching a node in a Binary Tree. How can I find the parent of the Node whose KEY is provided as an argument?

Here is the code for Normal search for a Binary Tree -

struct Tree* search(struct Tree *root, int KEY)
{
    struct Tree *temp;
    if(root == NULL) return NULL; //Base condition
    else
    {
        if(root-> data == KEY) return root;
        else
        {
            temp = search(root-> Lchild, KEY);
            if(temp != NULL) return temp;
            else return(search(root-> Rchild, KEY));
        }
    }
    return NULL;
}

Answer 1

You are returning the address of the Tree node whose value matches with the KEY , not it's parent. Assuming that all the node values are distinct in this tree, you have to follow the below code to return the parent Tree node address if it's child node (left or right child) value matches with the KEY .

struct Tree* search(struct Tree *root, int KEY){
    if(root == NULL){
        return NULL;
    }
    if(root->Lchild != NULL && root->Lchild->data == KEY){
        return root;
    }
    if(root->Rchild != NULL && root->Rchild->data == KEY){
        return root;
    }
    struct Tree *left = search(root->Lchild, KEY);
    struct Tree *right = search(root->Rchild, KEY);
    if(left != NULL){
        return left;
    }else if(right != NULL){
        return right;
    }
    return NULL;
}