二叉树后序遍历的非递归算法的c++代码

下面是二叉树后序遍历的非递归算法的 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) {}
};

void postorderTraversal(TreeNode* root) {
    if (!root) return;
    stack<TreeNode*> s1, s2;
    s1.push(root);
    while (!s1.empty()) {
        TreeNode* cur = s1.top();
        s1.pop();
        s2.push(cur);
        if (cur->left) s1.push(cur->left);
        if (cur->right) s1.push(cur->right);
    }
    while (!s2.empty()) {
        cout << s2.top()->val << " ";
        s2.pop();
    }
}

int main() {
    // create a binary tree
    TreeNode* root = new TreeNode(1);
    root->left = new TreeNode(2);
    root->right = new TreeNode(3);
    root->left->left = new TreeNode(4);
    root->left->right = new TreeNode(5);
    root->right->left = new TreeNode(6);
    root->right->right = new TreeNode(7);

    // postorder traversal
    cout << "Postorder Traversal: ";
    postorderTraversal(root);

    return 0;
}

这里采用两个栈的方法，第一个栈 s1 用于遍历二叉树，每次遍历到一个节点，将其入栈 s2，并将其左右子节点入栈 s1。当 s1 为空时，遍历结束，最后按照 s2 的顺序输出节点值即可。