#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <time.h>

#define TREE_TYPE int

typedef struct TREE_NODE {
    TREE_TYPE value;
    struct TREE_NODE *left;
    struct TREE_NODE *right;
}TreeNode;

static TreeNode *tree = NULL;

void insert(TREE_TYPE value)
{
    TreeNode *current;
    TreeNode **link;

    link = &tree;

    while((current = *link) != NULL) {
        if (value < current->value)    
            link = &current->left;
        else {
            link = &current->right;    
        }
    }

    current = malloc(sizeof(TreeNode));
    assert(current != NULL);
    current->value = value;
    current->left = NULL;
    current->right = NULL;
    current->right = NULL;
    *link = current;
}

TreeNode *find(TreeNode *current, TREE_TYPE value)
{
    while(current != NULL && current->value != value) {
        if (value < current->value)    
            current = current->left;
        else 
            current = current->right;
    }

    if (current != NULL)
        return current;
    else 
        return NULL;
}

void delete(TREE_TYPE value)
{
    TreeNode *current;
    TreeNode **link;

    link = &tree;

    while((current = *link) != NULL && value != current->value) {
        if (value < current->value)    
            link = &current->left;
        else
            link = &current->right;
    }
    assert(current != NULL);

    if (current->left == NULL && current->right == NULL) {
        *link = NULL;
        free(current);
    }
    else if (current->left == NULL || current->right == NULL) {
        if (current->left != NULL)    
            *link = current->left;
        else
            *link = current->right;
        free(current);
    }
    else {//左右子樹都不為空
        TreeNode *this_child;
        TreeNode *next_child;
        
        /*轉左，然後向右到盡頭*/
        this_child = current;
        next_child = this_child->left;
        while (next_child->right != NULL) {
            this_child = next_child;
            next_child = next_child->right;
        }

        current->value = next_child->value;
        if (this_child != current)
            this_child->right = next_child->left;
        else
            this_child->left = next_child->left;
        free(next_child);
    }
        
}

static void pre_order_traverse(TreeNode *current,
        void (*callback)(TREE_TYPE value))
{
    if (current != NULL) {
        callback(current->value);
        pre_order_traverse(current->left, callback);
        pre_order_traverse(current->right, callback);
    }
}

void print_tree(TREE_TYPE value)
{
    printf("%3d", value);
}

void inner_order_traverse(TreeNode *current,
        void (*callback)(TREE_TYPE value))
{
    if (current != NULL) {
        inner_order_traverse(current->left, callback);
        callback(current->value);
        inner_order_traverse(current->right, callback);
    }
}

void post_order_traverse(TreeNode *current,
        void (*callback)(TREE_TYPE value))
{
    if (current != NULL) {
        post_order_traverse(current->left, callback);
        post_order_traverse(current->right, callback);
        callback(current->value);
    }
}

int main(int argc, char *argv[])
{
    TreeNode *p;
    srand(time(NULL));
    int i = 0, value = 0;
    for (i = 0; i < 5; i++) {
        value = rand() % 100;
        insert(i);
    }
//    pre_order_traverse(tree, print_tree); //前序
    inner_order_traverse(tree, print_tree); //中序
    printf("\n");
//    post_order_traverse(tree, print_tree); //後序

    delete(1);   //刪除某個節點
    inner_order_traverse(tree, print_tree);
    return 0;
}