[英]Nonrecursive/Iterative Binary Search Tree in C (Homework)
如何使用C中的迭代算法在二叉搜索树中创建/删除节点?
BST中的迭代插入和删除
struct bst {
int data;
struct bst *left;
struct bst *right;
};
typedef struct bst bst_t;
bst_t *get_new_node(int val)
{
bst_t *node = (bst_t *) malloc(sizeof(bst_t));
node->data = val;
node->left = NULL;
node->right= NULL;
return node;
}
bst_t *insert(bst_t *root, int val)
{
if(!root) return get_new_node(val);
bst_t *prev = NULL, *ptr = root;
char type = ' ';
while(ptr) {
prev = ptr;
if(val < ptr->data) {
ptr = ptr->left;
type = 'l';
} else {
ptr = ptr->right;
type = 'r';
}
}
if(type == 'l')
prev->left = get_new_node(val);
else
prev->right = get_new_node(val);
return root;
}
int find_minimum_value(bst_t *ptr)
{
int min = ptr ? ptr->data : 0;
while(ptr) {
if(ptr->data < min) min = ptr->data;
if(ptr->left) {
ptr = ptr->left;
} else if(ptr->right) {
ptr = ptr->right;
} else ptr = NULL;
}
return min;
}
bst_t *delete(bst_t *root, int val)
{
bst_t *prev = NULL, *ptr = root;
char type = ' ';
while(ptr) {
if(ptr->data == val) {
if(!ptr->left && !ptr->right) { // node to be removed has no children's
if(ptr != root && prev) { // delete leaf node
if(type == 'l')
prev->left = NULL;
else
prev->right = NULL;
} else root = NULL; // deleted node is root
} else if (ptr->left && ptr->right) { // node to be removed has two children's
ptr->data = find_minimum_value(ptr->right); // find minimum value from right subtree
val = ptr->data;
prev = ptr;
ptr = ptr->right; // continue from right subtree delete min node
type = 'r';
continue;
} else { // node to be removed has one children
if(ptr == root) { // root with one child
root = root->left ? root->left : root->right;
} else { // subtree with one child
if(type == 'l')
prev->left = ptr->left ? ptr->left : ptr->right;
else
prev->right = ptr->left ? ptr->left : ptr->right;
}
}
free(ptr);
}
prev = ptr;
if(val < ptr->data) {
ptr = ptr->left;
type = 'l';
} else {
ptr = ptr->right;
type = 'r';
}
}
return root;
}
好贴。 只是一个建议。 我相信,在BST中找到最小值不必遍历正确的子树。 最小值必须在左子树上或在节点本身上(如果左子树为null)。 如果删除了正确的子树遍历,则可以优化函数find_minimum_value。
int find_minimum_value(bst_t *ptr)
{
while(ptr->left) {
ptr = ptr->left;
}
return ptr->data;
}
迭代插入:
struct tree_node *Insert_Element (struct tree_node *root, void *key, void *data) {
struct tree_node *new_node, *node;
node = root;
do {
switch (compare(key, node->key)) {
case -1: {
if (node->left == NULL) {
if ((new_node = create_node(key, data)) == NULL) {
return NULL;
}
node->left = new_node;
return new_node;
}
node = node->left;
} break;
case 1: {
if (node->right == NULL) {
if ((new_node = create_node(key, data)) == NULL) {
return NULL;
}
node->right = new_node;
return new_node;
}
node = node->right;
} break;
default: {
return node;
}
}
} while (node != NULL);
return NULL;
}
在C语言中,您可以将树中的指针intptr_t
为intptr_t
类型,并对它们执行按位操作。
遍历树时,可以通过将其与遍历的指针进行异或来存储节点的“父”指针。 然后,可以通过使用修改后的指针对来自您的节点的地址进行异或来遍历树。
可以在http://sites.google.com/site/debforit/efficiency-binary-tree-traversal-with-two-pointers中找到这种传统技术的有效示例
有了遍历树而无需递归的能力,您就可以基于遍历树来创建任何算法的迭代版本。
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