二叉查找树

#include <stdio.h>#include <stdlib.h>struct node{int data;struct node *parent;struct node *left;struct node *right;};struct tree{struct node *root;};/* 创建一个结点 */struct node *node_alloc(int val){struct node *ret = (struct node *) malloc(sizeof(struct node));ret->data        = val;ret->parent      = NULL;ret->left        = NULL;ret->right       = NULL;return ret;}/* 销毁一个结点 */void node_dealloc(struct node *n){n->parent = NULL;n->left   = NULL;n->right  = NULL;free(n);}/* 销毁整个子树 */void node_destroy(struct node *n){if (n->left != NULL){node_destroy(n->left);}if (n->right != NULL){node_destroy(n->right);}node_dealloc(n);}/* 返回子树中最小的元素 */struct node *node_minimum(struct node *n){while (n->left != NULL){n = n->left;}return n;}/* 返回子树中最大的元素 */struct node *node_maximum(struct node *n){while (n->right != NULL){n = n->right;}return n;}/* 查找结点在中序遍历序列中的前趋 */struct node *node_predecessor(struct node *n){struct node *ret;if (n->left != NULL){return node_maximum(n->left);}else{ret = n->parent;while (ret != NULL && ret->left == n){n   = ret;ret = n->parent;}}return ret;}/* 查找结点在中序遍历序列中的后继 */struct node *node_successor(struct node *n){struct node *ret;if (n->right != NULL){return node_minimum(n->right);}else{ret = n->parent;while (ret != NULL && ret->right == n){n   = ret;ret = n->parent;}}return ret;}/* 输出子树的中序遍历序列 */void node_inorder_traversal(struct node *n){if (n->left != NULL){node_inorder_traversal(n->left);}printf("%d ", n->data);if (n->right != NULL){node_inorder_traversal(n->right);}}/* 插入 */void tree_insert(struct tree *t, int val){struct node *parent = NULL;struct node *child  = t->root;/* 查找应该插入的位置parent */while (child != NULL){parent = child;if (val < child->data){child = child->left;}else{child = child->right;}}/* 如果parent == NULL说明为空树 */if (parent == NULL){t->root = node_alloc(val);}else{child = node_alloc(val);child->parent = parent;if (val < parent->data){parent->left = child;}else{parent->right = child;}}}/* 删除 */void tree_erase(struct tree *t, struct node *n){struct node *del;struct node *child;if (n == NULL){return;}/* 查找应该删除的结点del，del最多只有一个子结点 */if (n->left == NULL || n->right == NULL){del = n;}else{del = node_successor(n);/* 若待删除的结点不为n，将待删除结点的数据赋给n */n->data = del->data;}/* 调整子节点的父结点指针 */if (del->left != NULL){child = del->left;}else{child = del->right;}if (child != NULL){child->parent = del->parent;}/* 若父结点为NULL，说明待删除的结点为树的根结点，此时需要重新调整树的根结点 */if (del->parent == NULL){t->root = child;}/* 调整父结点的子结点指针 */else if (del->parent->left == del){del->parent->left = child;}else{del->parent->right = child;}/* 销毁结点 */node_dealloc(del);}/* 查找，返回中序遍历序列中第一个匹配的 */struct node *tree_search(struct tree *t, int val){struct node *ret = t->root;while (ret != NULL){if (val == ret->data){break;}else if (val < ret->data){ret = ret->left;}else{ret = ret->right;}}return ret;}/* 树结构初始化 */void tree_init(struct tree *t){t->root = NULL;}/* 销毁整棵树 */void tree_destroy(struct tree *t){if (t->root != NULL){node_destroy(t->root);t->root = NULL;}}/* 输出树的中序遍历序列 */void tree_inorder_traversal(struct tree *t){if (t->root != NULL){node_inorder_traversal(t->root);printf("\n");}}int main(void){struct tree t;struct node *n;tree_init(&t);tree_insert(&t, 1);tree_insert(&t, 2);tree_insert(&t, 3);tree_insert(&t, 4);tree_insert(&t, 5);tree_inorder_traversal(&t);n = tree_search(&t, 1);tree_erase(&t, n);tree_inorder_traversal(&t);n = tree_search(&t, 3);tree_erase(&t, n);tree_inorder_traversal(&t);n = tree_search(&t, 4);tree_erase(&t, n);tree_inorder_traversal(&t);tree_destroy(&t);return 0;}