插入完整的二叉樹

Question

我正在嘗試為學校作業插入一個完整的二叉樹。 我的樹的結構是這樣的

typedef struct TreeNode {
void * data;
struct TreeNode * left;
struct TreeNode * right;
struct TreeNode * parent;
} TNode;

typedef struct CompleteBinaryTree {
TNode * root;
TNode * last;
int numelm;
} CBTree;

根據情況，我有 4 種插入方式

• 樹是空的
• 樹作為一個節點
• CBT的最后一個節點是他的父母的左孩子
• 最后我上樹，只要當前節點是他父節點的右節點，如果當前節點不是根節點，我會去找他的兄弟然后向左向下，否則我就向左向下

我目前被困在我的第三種方式上，我不知道我的代碼有什么問題。

有人能把我推向正確的方向嗎？

謝謝 ！

void CBTreeInsert(CBTree* tree, void* data) {
    TNode * tmp = newTNode(data);
    TNode * curr = tree->last;

    if(tree->root == NULL) //empty
    { 
        tree->root = tmp;
    }
    else if(tree->last == tree->root) //one node
    {
        tree->last->left = tmp;
    }
    else if(tree->last->parent->right == NULL) //general
    {
        tree->last->parent->right = tmp;
    }
    else if(tree->last->parent == tree->last->parent->right) //degenarated
    {
        while(curr->parent == curr->parent->right)
                curr = curr->parent;

        if(curr != tree->root)
        {
            curr = curr->parent->right;
            while(curr->left != NULL)
                curr = curr->left;
        }
        curr->left = tmp;
        }
    else
        {
            while(curr->left != NULL)
                curr = curr->left;

            curr->left = tmp;
        }
}
else
{
    fprintf(stderr,"Error\n");
}

tree->last = tmp;
tree->numelm++;
}

Answer 1

我想你或多或少有它，但是：

1. 我沒有看到新節點的tmp->parent設置在哪里？

2. else if(tree->last->parent == tree->last->parent->right)壞了，我覺得這應該是else if(tree->last == tree->last->parent->right) ，在這一點上這絕對是正確的。

3. while(curr->parent == curr->parent->right) curr = curr->parent; curr == tree->root可能有問題，盡管可以通過設置tree->root->parent = tree->root

4. 你有兩份：

    while(curr->left != NULL)
    {
        curr = curr->left;
    }
    curr->left = tmp;`

我很想這樣做：

else if (tree->last == tree->last->parent->right)
{
    TNode * curr = tree->last->parent ; // NB: know that tree->last != tree->root
                                        //     so can step up.  
    while (1)
    {
        if (curr == tree->root)
            break ;

        if (curr == curr->parent->left)
        {
            // The parent of the curr node is to the right of the last node, so
            // step to its right, and then insert to the extreme left of that.
            curr = curr->parent->right ;
            assert(curr != NULL) ;
            break ;
        } ;
        curr = curr->parent ;
    } ;

    // Arrive here with curr as root of sub-tree in which now want to insert the
    // new node as the left-most child.

    while (curr->left != NULL)
    {
        assert(curr->right != NULL) ;
        curr = curr->left ;
    } ;
    assert(curr->right == NULL) ;
    tmp->parent = curr ;
    curr->left  = tree->last = tmp;
}

但我沒有測試過這個。 （還有其他地方需要設置tmp->parent 。）