C语言实现二叉搜索树的创建、插入、删除和查找

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#define TREE_TYPE int
#define size 15

/**定义树形结构*/
typedef struct Tree
{
TREE_TYPE value;
struct Tree *left;
struct Tree *right;
}Tree_node;

/**根节点作为全局静态变量*/
static Tree_node *root;

/**初始化树*/
void create_tree()
{
root = NULL;
}

/**向树种插入数据*/
Tree_node* insert(Tree_node *node,TREE_TYPE value)
{
if(node == NULL)
{
node = (Tree_node*)malloc(sizeof(Tree_node) * 1);
node-> value = value;
node -> left = NULL;
node -> right = NULL;
if(root == NULL) //如果为根节点
root = node;
}
else
{
if(value < node->value) //比该节点值小，写向左子树
node->left = insert(node->left,value);
else //比该节点值大，写向右子树
node->right = insert(node->right,value);
}
return node;
}

/**显示树中所有节点内容*/
void show_all(Tree_node *node)
{
if(node != NULL)
{
if(node->left != NULL)
show_all(node->left);
printf("%d ",node->value);
if(node->right != NULL);
show_all(node->right);
}
}

/**根据值查找某一特定节点*/
Tree_node* search(Tree_node *node,TREE_TYPE value)
{
Tree_node *result = NULL;
if(node != NULL)
{
if(value == node->value)
result = node;
else if(value < node->value)
result = search(node->left,value);
else
result = search(node->right,value);
}
return result;
}

/**找到某一值对应节点的父节点*/
Tree_node* find_parent(Tree_node *parent,TREE_TYPE value)
{
Tree_node *result = NULL;
if(parent != NULL)
{
if(value < parent->value && parent->left != NULL) //比父节点值小，访问左子树
{
if(value == parent->left->value)
result = parent;
else
{
result = find_parent(parent->left,value);
if(result == NULL)
result = find_parent(parent->right,value);
}
}
if(value > parent->value && parent->right != NULL) //比父节点值大，访问右子树
{
if(value == parent->right->value)
result = parent;
else
{
result = find_parent(parent->left,value);
if(result == NULL)
result = find_parent(parent->right,value);
}
}
}
return result;
}

void delete(TREE_TYPE value)
{
Tree_node *parent = find_parent(root,value); //找到待删节点的父节点
Tree_node *node = search(root,value); //找到待删节点
if(node == NULL) //待删节点不存在
printf("没有待删节点\n");
else //待删节点存在
{
if(node->left == NULL && node->right == NULL) //如果待删节点是叶子节点
{
// assert(parent != NULL);
if(parent == NULL) //如果是根节点
root = NULL;
else //其他节点
{
if(node == parent->left)
parent->left = NULL;
else
parent->right = NULL;
}
}
else if(node->right == NULL) //如果待删节点只有左子树节点
{
if(parent == NULL) //如果是根节点
root = node->left;
else //其他节点
{
if(node == parent->left)
parent->left = node->left;
else
parent->right = node->left;
}
}
else if(node->left == NULL) //如果待删节点只有右子树节点
{
if(parent == NULL) //如果是根节点
root = node->right;
else //其他节点
{
if(node == parent->left)
parent->left = node->right;
else
parent->right = node->right;
}
}
else //如果带删节点左右子树节点都存在
{
Tree_node *new_node = node->right; //需要找到右子树的最左那个
Tree_node *new_node_parent = NULL;
while(new_node->left != NULL)
{
new_node_parent = new_node;
new_node = new_node->left;
}
if(new_node != node->left)
new_node->left = node->left;
if(new_node != node->right)
new_node->right = node->right;
if(parent == NULL)
root = new_node;
else
{
if(node == parent->left) //如果带删节点是父节点的左节点
parent->left = new_node;
else //如果待删节点是父节点的右节点
parent->right = new_node;
}
if(new_node_parent != NULL)//将原来的右子树最左节点删掉
new_node_parent->left = NULL;
}
}
}

int main()
{
/**初始化*/
create_tree();

/**插入*/
TREE_TYPE list[size] = {8,4,11,2,6,10,13,1,3,5,7,9,15,14,16};
int i;
for(i = 0; i < size; i++)
insert(root,list[i]);

/**显示全部*/
show_all(root);
putchar('\n');

/**根据值查找某节点*/
Tree_node *result = search(root,14);
if(result != NULL)
printf("To find %d,result is %d\n",14,result->value);
else
printf("Not find\n");

/**根据值查找其父节点*/
Tree_node *parent_result = find_parent(root,14);
if(parent_result != NULL)
printf("To find %d's parent,result is %d\n",14,parent_result->value);
else
printf("Cannot find %d's parent\n",14);

/**删除*/
delete(14); //删除叶子节点
show_all(root);
putchar('\n');
delete(13); //删除只有右子树的节点
show_all(root);
putchar('\n');
delete(11); //删除只有左子树的节点
show_all(root);
putchar('\n');
delete(4); //删除左右子树都有的节点
show_all(root);
putchar('\n');

return 0;
}