C语言实现根据key值进行二叉树的增删查改

1. 增加节点：

struct TreeNode* insert(struct TreeNode* root, int key) {
    if (root == NULL) {
        return createNode(key);
    }
    if (key < root->key) {
        root->left = insert(root->left, key);
    } else if (key > root->key) {
        root->right = insert(root->right, key);
    }
    return root;
}

2. 删除节点：

struct TreeNode* delete(struct TreeNode* root, int key) {
    if (root == NULL) {
        return root;
    }
    if (key < root->key) {
        root->left = delete(root->left, key);
    } else if (key > root->key) {
        root->right = delete(root->right, key);
    } else {
        if (root->left == NULL) {
            struct TreeNode* temp = root->right;
            free(root);
            return temp;
        } else if (root->right == NULL) {
            struct TreeNode* temp = root->left;
            free(root);
            return temp;
        }
        struct TreeNode* temp = minValueNode(root->right);
        root->key = temp->key;
        root->right = delete(root->right, temp->key);
    }
    return root;
}

3. 查找节点：

struct TreeNode* search(struct TreeNode* root, int key) {
    if (root == NULL || root->key == key) {
        return root;
    }
    if (key < root->key) {
        return search(root->left, key);
    }
    return search(root->right, key);
}

4. 修改节点：

struct TreeNode* modify(struct TreeNode* root, int oldKey, int newKey) {
    root = delete(root, oldKey);
    root = insert(root, newKey);
    return root;
}