Question

如何在C？

中使用迭代算法在二叉搜索树中创建/删除节点

Answer 1

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;
}

Answer 2

迭代插入＆amp;在BST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;
}

Answer 3

好帖子。只是一个建议。我相信，在BST中找到最小值并不必遍历正确的子树。最小值必须位于左子树或节点本身（如果左子树为空，则为最小值）。如果删除了右子树遍历，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;
}

Answer 4

在C中，您可以将树中的指针强制转换为intptr_t类型，并对它们执行按位操作。

当您遍历树时，可以通过使用您遍历的指针对其进行xoring来存储节点的“父”指针。然后，您可以通过使用修改后的指针对您来自的节点的地址进行编辑来遍历树。

这种传统技术的一个有效例子是http://sites.google.com/site/debforit/efficient-binary-tree-traversal-with-two-pointers

鉴于能够在没有递归的情况下遍历树，您可以基于遍历树创建任何算法的迭代版本。

C中的非递归/迭代二进制搜索树（家庭作业）

4 个答案: