二叉排序树非递归遍历代码c++

以下是二叉排序树的先序、中序和后序非递归遍历的C++代码：

#include <iostream>
#include <stack>
using namespace std;

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

// 先序遍历
void preOrder(TreeNode* root) {
    if (root == NULL) {
        return;
    }
    stack<TreeNode*> s;
    s.push(root);
    while (!s.empty()) {
        TreeNode* node = s.top();
        s.pop();
        cout << node->val << " ";
        if (node->right != NULL) {
            s.push(node->right);
        }
        if (node->left != NULL) {
            s.push(node->left);
        }
    }
}

// 中序遍历
void inOrder(TreeNode* root) {
    if (root == NULL) {
        return;
    }
    stack<TreeNode*> s;
    TreeNode* node = root;
    while (node != NULL || !s.empty()) {
        while (node != NULL) {
            s.push(node);
            node = node->left;
        }
        node = s.top();
        s.pop();
        cout << node->val << " ";
        node = node->right;
    }
}

// 后序遍历
void postOrder(TreeNode* root) {
    if (root == NULL) {
        return;
    }
    stack<TreeNode*> s1, s2;
    s1.push(root);
    while (!s1.empty()) {
        TreeNode* node = s1.top();
        s1.pop();
        s2.push(node);
        if (node->left != NULL) {
            s1.push(node->left);
        }
        if (node->right != NULL) {
            s1.push(node->right);
        }
    }
    while (!s2.empty()) {
        cout << s2.top()->val << " ";
        s2.pop();
    }
}

int main() {
    TreeNode* root = new TreeNode(5);
    root->left = new TreeNode(3);
    root->right = new TreeNode(7);
    root->left->left = new TreeNode(2);
    root->left->right = new TreeNode(4);
    root->right->left = new TreeNode(6);
    root->right->right = new TreeNode(8);

    cout << "Preorder traversal: ";
    preOrder(root);
    cout << endl;

    cout << "Inorder traversal: ";
    inOrder(root);
    cout << endl;

    cout << "Postorder traversal: ";
    postOrder(root);
    cout << endl;

    return 0;
}