插入函数重新创建根节点

Question

我正在尝试创建一个非递归的 insert() 函数。我在书中唯一的例子是一个递归的例子，我正在尝试转换它。只是为了让您了解我要完成的工作以及我为什么要包含这些说明。

编写一个类来实现一个能够存储数字的简单二叉搜索树。类应该有成员函数：

void insert(double x)
bool search(double x)
void inorder(vector <double> & v)

插入函数不应直接或通过调用递归函数间接使用递归。

还有更多，但我认为这给出了我所问问题背后的想法。截至目前，该功能只是继续重新创建根节点。这是我所拥有的。

#include "stdafx.h"
#include <iostream>
#include <vector>

class BinaryTree {

private:
struct TreeNode {

    double value;
    TreeNode *left;
    TreeNode *right;
    TreeNode(double value1,
        TreeNode *left1 = nullptr,
        TreeNode *right1 = nullptr) {

        value = value1;
        left = left1;
        right = right1;
    }
};

TreeNode *root;    //pointer to the root of the tree
bool search(double x, TreeNode *t) {

    while (t) {
        std::cout << "running through t." << std::endl;
        if (t->value == x) {
            return true;
        }
        else if (x < t->value) {
            std::cout << "wasn't found, moving left." << std::endl;
            search(x, t->left);
        }
        else {
            std::cout << "wasn't found, moving right." << std::endl;
            search(x, t->right);
        }
    }
    std::cout << "wasn't found." << std::endl;
    return false;
}


public:

std::vector<TreeNode> v;

BinaryTree() {
    root = nullptr;
}

void insert(double x) {
    TreeNode *tree = root;

    if (!tree) {
        std::cout << "Creating tree." << x << std::endl;
        root = new TreeNode(x);
        return;
    }

    while (tree) {

        std::cout << "Adding next value." << std::endl;
        if (tree->value == x) return;

        if (x < tree->value) {
            tree = tree->left;
            tree->value = x;
        }
        else {
            tree = tree->right;
            tree->value = x;
        }
    }

}
bool search(double x) {

    return search(x, root);
}

/*void inOrder(TreeNode *v) const {

    while (root != nullptr) {

        inOrder(root->left);
        v.push_back(root->value);
        inOrder(root->right);
        v.push_back(root->value);
    }
}*/
};

int main() {

    BinaryTree t;

    std::cout << "Inserting the numbers 5, 8, 3, 12, and 9." << std::endl;
    t.insert(5);
    t.insert(8);
    t.insert(3);
    t.insert(12);
    t.insert(9);

    std::cout << "Looking for 12 in tree." << std::endl;
    if (t.search(12)) {
        std::cout << "12 was found." << std::endl;
    }

    std::cout << "Here are the numbers in order." << std::endl;


    return 0;
}

Answer 1

如果您希望代码正常工作，您必须再添加一层取消引用。当然，在函数结束时创建新节点。以下代码应该可以工作：

void insert(double x) {
    TreeNode **tree = &root;

    while (*tree) {
        std::cout << "Adding next value." << std::endl;
        if ((*tree)->value == x) return;

        if (x < (*tree)->value) {
            tree = &(*tree)->left;
        } else {
            tree = &(*tree)->right;
        }
    }

    if (!(*tree)) {
        std::cout << "Creating tree." << x << std::endl;
        *tree = new TreeNode(x);
        return;
    }
}

你的search 方法应该是这样的：

bool search(double x) {
    TreeNode *node = root;

    while (node) {
        if (node->value == x) {
            return true;
        } else if (x < node->value) {
            node = node->left;
        } else {
            node = node->right;
        }
    }

    std::cout << "wasn't found." << std::endl;
    return false;
}

你的主要功能的结果，我的代码：

Inserting the numbers 5, 8, 3, 12, and 9.
Creating tree.5
Adding next value.
Creating tree.8
Adding next value.
Creating tree.3
Adding next value.
Adding next value.
Creating tree.12
Adding next value.
Adding next value.
Adding next value.
Creating tree.9
Looking for 12 in tree.
12 was found.