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<bits\stdc++.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 }
