自下而上，从右至左的层序遍历

普通的层序遍历是自下而上，从左至右； 这里刚好相反， 对于这样的问题，一般采用栈，栈能够实现序列的逆序。      因此，普通的层序遍历+栈，就能够解决这个问题。

#include<bitsstdc++.h>
using namespace std;

struct node {
    int data;
    node* left = nullptr, * right = nullptr;
};

typedef struct node Node;

Node* CreateTree() {
    Node* root = new Node;
    root->data = 1;
    root->left = new Node;
    root->left->data = 2;
    root->right = new Node;
    root->right->data = 3;
    root->left->left = new Node;
    root->left->left->data = 4;
    root->left->right = new Node;
    root->left->right->data = 5;
    root->right->left = new Node;
    root->right->left->data = 6;
    root->right->right = new Node;
    root->right->right->data = 7;
    return root;
}

// 
void ReverseLevelTravel(Node* root) {
    if (root != nullptr) {
        queue<Node*> q;
        stack<Node*> s;
        q.push(root);

        while (!q.empty()) {
            root = q.front();
            s.push(root);   // 将出队的元素放入栈中
            q.pop();
            if (root->left != nullptr) {
                q.push(root->left);
            }
            if (root->right != nullptr) {
                q.push(root->right);
            }
        }

        while (!s.empty()) {
            root = s.top();
            s.pop();
            cout << root->data << " ";
        }
    }
}

int main() {
    Node* root = CreateTree();
    ReverseLevelTravel(root);
    return 0;
}