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2.4 刪除節點的左右子樹都存在，此時又會分成兩種情形
1）左節點是當前左子樹的最大節點，此時只需要用左節點代替根節點即可
/*
*
* 10 ======> 6
* / \ / \
* 6 15 5 15
* /
* 5
*/
/*
*
* 10 ======> 6
* / \ / \
* 6 15 5 15
* /
* 5
*/ 代碼該怎麼編寫呢？
STATUS delete_node_from_tree(TREE_NODE** ppTreeNode, int data)
{
TREE_NODE* pTreeNode;
TREE_NODE* pLeftMax;
if(NULL == ppTreeNode || NULL == *ppTreeNode)
return FALSE;
pTreeNode = find_data_in_tree_node(*ppTreeNode, data);
if(NULL == pTreeNode)
return FALSE;
if(*ppTreeNode == pTreeNode){
if(NULL == pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = NULL;
}else if(NULL != pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = pTreeNode->left_child;
pTreeNode->left_child->parent = NULL;
}else if(NULL == pTreeNode->left_child && NULL != pTreeNode->right_child){
*ppTreeNode = pTreeNode->right_child;
pTreeNode->right_child->parent = NULL;
}else{
pLeftMax = find_max_node(pTreeNode->left_child);
if(pLeftMax == pTreeNode->left_child){
*ppTreeNode = pTreeNode->left_child;
(*ppTreeNode)->right_child = pTreeNode->right_child;
(*ppTreeNode)->right_child->parent = *ppTreeNode;
(*ppTreeNode)->parent = NULL;
}
}
free(pTreeNode);
return TRUE;
}
return TRUE;
}
STATUS delete_node_from_tree(TREE_NODE** ppTreeNode, int data)
{
TREE_NODE* pTreeNode;
TREE_NODE* pLeftMax;
if(NULL == ppTreeNode || NULL == *ppTreeNode)
return FALSE;
pTreeNode = find_data_in_tree_node(*ppTreeNode, data);
if(NULL == pTreeNode)
return FALSE;
if(*ppTreeNode == pTreeNode){
if(NULL == pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = NULL;
}else if(NULL != pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = pTreeNode->left_child;
pTreeNode->left_child->parent = NULL;
}else if(NULL == pTreeNode->left_child && NULL != pTreeNode->right_child){
*ppTreeNode = pTreeNode->right_child;
pTreeNode->right_child->parent = NULL;
}else{
pLeftMax = find_max_node(pTreeNode->left_child);
if(pLeftMax == pTreeNode->left_child){
*ppTreeNode = pTreeNode->left_child;
(*ppTreeNode)->right_child = pTreeNode->right_child;
(*ppTreeNode)->right_child->parent = *ppTreeNode;
(*ppTreeNode)->parent = NULL;
}
}
free(pTreeNode);
return TRUE;
}
return TRUE;
} 上面的代碼中添加的內容表示了我們介紹的這一情形。為此，我們可以設計一種測試用例。依次插入10、6、5、15，然後刪除10即可。
static void test6()
{
TREE_NODE* pTreeNode = NULL;
assert(TRUE == insert_node_into_tree(&pTreeNode, 10));
assert(TRUE == insert_node_into_tree(&pTreeNode, 6));
assert(TRUE == insert_node_into_tree(&pTreeNode, 5));
assert(TRUE == insert_node_into_tree(&pTreeNode, 15));
assert(TRUE == delete_node_from_tree(&pTreeNode, 10));
assert(6 == pTreeNode->data);
assert(NULL == pTreeNode->parent);
assert(15 == pTreeNode->right_child->data);
assert(pTreeNode = pTreeNode->right_child->parent);
assert(NULL == pTreeNode->parent);
free(pTreeNode->left_child);
free(pTreeNode->right_child);
free(pTreeNode);
}
static void test6()
{
TREE_NODE* pTreeNode = NULL;
assert(TRUE == insert_node_into_tree(&pTreeNode, 10));
assert(TRUE == insert_node_into_tree(&pTreeNode, 6));
assert(TRUE == insert_node_into_tree(&pTreeNode, 5));
assert(TRUE == insert_node_into_tree(&pTreeNode, 15));
assert(TRUE == delete_node_from_tree(&pTreeNode, 10));
assert(6 == pTreeNode->data);
assert(NULL == pTreeNode->parent);
assert(15 == pTreeNode->right_child->data);
assert(pTreeNode = pTreeNode->right_child->parent);
assert(NULL == pTreeNode->parent);
free(pTreeNode->left_child);
free(pTreeNode->right_child);
free(pTreeNode);
} 如果上面的測試用例通過，表示我們添加的代碼沒有問題。
2）左節點不是當前左子樹的最大節點，情形如下所示
/*
*
* 10 ======> 8
* / \ / \
* 6 15 5 15
* \
* 8
*/
/*
*
* 10 ======> 8
* / \ / \
* 6 15 5 15
* \
* 8
*/ 此時，我們應該用10左側的最大節點8代替刪除的節點10即可。
STATUS delete_node_from_tree(TREE_NODE** ppTreeNode, int data)
{
TREE_NODE* pTreeNode;
TREE_NODE* pLeftMax;
if(NULL == ppTreeNode || NULL == *ppTreeNode)
return FALSE;
pTreeNode = find_data_in_tree_node(*ppTreeNode, data);
if(NULL == pTreeNode)
return FALSE;
if(*ppTreeNode == pTreeNode){
if(NULL == pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = NULL;
}else if(NULL != pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = pTreeNode->left_child;
pTreeNode->left_child->parent = NULL;
}else if(NULL == pTreeNode->left_child && NULL != pTreeNode->right_child){
*ppTreeNode = pTreeNode->right_child;
pTreeNode->right_child->parent = NULL;
}else{
pLeftMax = find_max_node(pTreeNode->left_child);
if(pLeftMax == pTreeNode->left_child){
*ppTreeNode = pTreeNode->left_child;
(*ppTreeNode)->right_child = pTreeNode->right_child;
(*ppTreeNode)->right_child->parent = *ppTreeNode;
(*ppTreeNode)->parent = NULL;
}else{
pTreeNode->data = pLeftMax->data;
pLeftMax->parent->right_child = NULL;
pTreeNode = pLeftMax;
}
}
free(pTreeNode);
return TRUE;
}
return TRUE;
}
STATUS delete_node_from_tree(TREE_NODE** ppTreeNode, int data)
{
TREE_NODE* pTreeNode;
TREE_NODE* pLeftMax;
if(NULL == ppTreeNode || NULL == *ppTreeNode)
return FALSE;
pTreeNode = find_data_in_tree_node(*ppTreeNode, data);
if(NULL == pTreeNode)
return FALSE;
if(*ppTreeNode == pTreeNode){
if(NULL == pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = NULL;
}else if(NULL != pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = pTreeNode->left_child;
pTreeNode->left_child->parent = NULL;
}else if(NULL == pTreeNode->left_child && NULL != pTreeNode->right_child){
*ppTreeNode = pTreeNode->right_child;
pTreeNode->right_child->parent = NULL;
}else{
pLeftMax = find_max_node(pTreeNode->left_child);
if(pLeftMax == pTreeNode->left_child){
*ppTreeNode = pTreeNode->left_child;
(*ppTreeNode)->right_child = pTreeNode->right_child;
(*ppTreeNode)->right_child->parent = *ppTreeNode;
(*ppTreeNode)->parent = NULL;
}else{
pTreeNode->data = pLeftMax->data;
pLeftMax->parent->right_child = NULL;
pTreeNode = pLeftMax;
}
}
free(pTreeNode);
return TRUE;
}
return TRUE;
} 那麼，這個場景下面測試用例又該怎麼設計呢？其實只需要按照上面給出的示意圖進行即可。依次插入數據10、6、8、15，然後刪除數據10。
static void test7()
{
TREE_NODE* pTreeNode = NULL;
assert(TRUE == insert_node_into_tree(&pTreeNode, 10));
assert(TRUE == insert_node_into_tree(&pTreeNode, 6));
assert(TRUE == insert_node_into_tree(&pTreeNode, 8));
assert(TRUE == insert_node_into_tree(&pTreeNode, 15));
assert(TRUE == delete_node_from_tree(&pTreeNode, 10));
assert(8 == pTreeNode->data);
assert(NULL == pTreeNode->parent);
assert(NULL == pTreeNode->left_child->right_child);
assert(NULL == pTreeNode->parent);
free(pTreeNode->left_child);
free(pTreeNode->right_child);
free(pTreeNode);
}
static void test7()
{
TREE_NODE* pTreeNode = NULL;
assert(TRUE == insert_node_into_tree(&pTreeNode, 10));
assert(TRUE == insert_node_into_tree(&pTreeNode, 6));
assert(TRUE == insert_node_into_tree(&pTreeNode, 8));
assert(TRUE == insert_node_into_tree(&pTreeNode, 15));
assert(TRUE == delete_node_from_tree(&pTreeNode, 10));
assert(8 == pTreeNode->data);
assert(NULL == pTreeNode->parent);
assert(NULL == pTreeNode->left_child->right_child);
assert(NULL == pTreeNode->parent);
free(pTreeNode->left_child);
free(pTreeNode->right_child);
free(pTreeNode);
} 至此，刪除節點為根節點的情形全部討論完畢，那麼如果刪除的節點是普通節點呢，那應該怎麼解決呢？
STATUS delete_node_from_tree(TREE_NODE** ppTreeNode, int data)
{
TREE_NODE* pTreeNode;
TREE_NODE* pLeftMax;
if(NULL == ppTreeNode || NULL == *ppTreeNode)
return FALSE;
pTreeNode = find_data_in_tree_node(*ppTreeNode, data);
if(NULL == pTreeNode)
return FALSE;
if(*ppTreeNode == pTreeNode){
if(NULL == pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = NULL;
}else if(NULL != pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = pTreeNode->left_child;
pTreeNode->left_child->parent = NULL;
}else if(NULL == pTreeNode->left_child && NULL != pTreeNode->right_child){
*ppTreeNode = pTreeNode->right_child;
pTreeNode->right_child->parent = NULL;
}else{
pLeftMax = find_max_node(pTreeNode->left_child);
if(pLeftMax == pTreeNode->left_child){
*ppTreeNode = pTreeNode->left_child;
(*ppTreeNode)->right_child = pTreeNode->right_child;
(*ppTreeNode)->right_child->parent = *ppTreeNode;
(*ppTreeNode)->parent = NULL;
}else{
pTreeNode->data = pLeftMax->data;
pLeftMax->parent->right_child = NULL;
pTreeNode = pLeftMax;
}
}
free(pTreeNode);
return TRUE;
}
return _delete_node_from_tree(pTreeNode);
}
STATUS delete_node_from_tree(TREE_NODE** ppTreeNode, int data)
{
TREE_NODE* pTreeNode;
TREE_NODE* pLeftMax;
if(NULL == ppTreeNode || NULL == *ppTreeNode)
return FALSE;
pTreeNode = find_data_in_tree_node(*ppTreeNode, data);
if(NULL == pTreeNode)
return FALSE;
if(*ppTreeNode == pTreeNode){
if(NULL == pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = NULL;
}else if(NULL != pTreeNode->left_child && NULL == pTreeNode->right_child){
*ppTreeNode = pTreeNode->left_child;
pTreeNode->left_child->parent = NULL;
}else if(NULL == pTreeNode->left_child && NULL != pTreeNode->right_child){
*ppTreeNode = pTreeNode->right_child;
pTreeNode->right_child->parent = NULL;
}else{
pLeftMax = find_max_node(pTreeNode->left_child);
if(pLeftMax == pTreeNode->left_child){
*ppTreeNode = pTreeNode->left_child;
(*ppTreeNode)->right_child = pTreeNode->right_child;
(*ppTreeNode)->right_child->parent = *ppTreeNode;
(*ppTreeNode)->parent = NULL;
}else{
pTreeNode->data = pLeftMax->data;
pLeftMax->parent->right_child = NULL;
pTreeNode = pLeftMax;
}
}
free(pTreeNode);
return TRUE;
}
return _delete_node_from_tree(pTreeNode);
} 我們在當前函數的最後一行添加_delete_node_from_tree，這個函數用來處理普通節點的刪除情況，我們會在下面一篇博客中繼續介紹。
3、 普通節點的刪除
