一步一步写算法（之排序二叉树删除-2）-优快云博客

本文详细阐述了在树结构中删除节点的具体实现，并通过测试用例验证了代码的正确性，包括删除根节点和普通节点的情况。

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2.4 删除节点的左右子树都存在，此时又会分成两种情形

1）左节点是当前左子树的最大节点，此时只需要用左节点代替根节点即可

/* * * 10 ======> 6 * / \ / \ * 6 15 5 15 * / * 5 */ 代码该怎么编写呢？

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; } 上面的代码中添加的内容表示了我们介绍的这一情形。为此，我们可以设计一种测试用例。依次插入10、6、5、15，然后删除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); } 如果上面的测试用例通过，表示我们添加的代码没有问题。

2）左节点不是当前左子树的最大节点，情形如下所示

/* * * 10 ======> 8 * / \ / \ * 6 15 5 15 * \ * 8 */ 此时，我们应该用10左侧的最大节点8代替删除的节点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; } 那么，这个场景下面测试用例又该怎么设计呢？其实只需要按照上面给出的示意图进行即可。依次插入数据10、6、8、15，然后删除数据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); } 至此，删除节点为根节点的情形全部讨论完毕，那么如果删除的节点是普通节点呢，那应该怎么解决呢？

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 = pLeftMax->left_child; pTreeNode = pLeftMax; } } free(pTreeNode); return TRUE; } return _delete_node_from_tree(pTreeNode); } 我们在当前函数的最后一行添加_delete_node_from_tree，这个函数用来处理普通节点的删除情况，我们会在下面一篇博客中继续介绍。

3、普通节点的删除

（待续）