二叉树中序线索遍历-526互联

#include <iostream>

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    bool leftThread;  // 标识左子树是否为线索
    bool rightThread; // 标识右子树是否为线索

    TreeNode(int value) : val(value), left(nullptr), right(nullptr), leftThread(false), rightThread(false) {}
};

// 中序线索化二叉树
void InorderThread(TreeNode* root, TreeNode*& prev) {
    if (root == nullptr) {
        return;
    }

    // 线索化左子树
    InorderThread(root->left, prev);

    // 处理当前节点
    if (root->left == nullptr) {
        root->left = prev;
        root->leftThread = true;
    }
    if (prev != nullptr && prev->right == nullptr) {
        prev->right = root;
        prev->rightThread = true;
    }
    prev = root;

    // 线索化右子树
    InorderThread(root->right, prev);
}

// 中序线索化遍历二叉树
void InorderThreadTraversal(TreeNode* root) {
    TreeNode* node = root;
    while (node != nullptr) {
        // 找到中序遍历的第一个节点，即最左下的节点
        while (node->left != nullptr && !node->leftThread) {
            node = node->left;
        }

        std::cout << node->val << " ";

        // 判断右指针类型
        if (node->rightThread) {
            node = node->right;
        } else {
            node = node->right;
            while (node != nullptr && !node->leftThread) {
                node = node->left;
            }
        }
    }
}

int main() {
    // 构建二叉树
    TreeNode* root = new TreeNode(4);
    root->left = new TreeNode(2);
    root->right = new TreeNode(6);
    root->left->left = new TreeNode(1);
    root->left->right = new TreeNode(3);
    root->right->left = new TreeNode(5);
    root->right->right = new TreeNode(7);

    // 执行中序线索化
    TreeNode* prev = nullptr;
    InorderThread(root, prev);

    // 中序线索化遍历
    InorderThreadTraversal(root);
    std::cout << std::endl;

    // 释放内存
    // ...
  
    return 0;
}