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。

 1 #include<bitsstdc++.h>
 2 using namespace std;
 3 
 4 struct node {
 5     int data;
 6     node* left = nullptr, * right = nullptr;
 7 };
 8 
 9 typedef struct node Node;
10 
11 Node* CreateTree() {
12     Node* root = new Node;
13     root->data = 1;
14     root->left = new Node;
15     root->left->data = 2;
16     root->right = new Node;
17     root->right->data = 3;
18     root->left->left = new Node;
19     root->left->left->data = 4;
20     root->left->right = new Node;
21     root->left->right->data = 5;
22     root->right->left = new Node;
23     root->right->left->data = 6;
24     root->right->right = new Node;
25     root->right->right->data = 7;
26     return root;
27 }
28 
29 // 
30 void ReverseLevelTravel(Node* root) {
31     if (root != nullptr) {
32         queue<Node*> q;
33         stack<Node*> s;
34         q.push(root);
35 
36         while (!q.empty()) {
37             root = q.front();
38             s.push(root);   // 将出队的元素放入栈中
39             q.pop();
40             if (root->left != nullptr) {
41                 q.push(root->left);
42             }
43             if (root->right != nullptr) {
44                 q.push(root->right);
45             }
46         }
47 
48         while (!s.empty()) {
49             root = s.top();
50             s.pop();
51             cout << root->data << " ";
52         }
53     }
54 }
55 
56 int main() {
57     Node* root = CreateTree();
58     ReverseLevelTravel(root);
59     return 0;
60 }