Chuyển ngang cây thứ tự cấp độ trong cấu trúc dữ liệu

Trong phần này, chúng ta sẽ thấy kỹ thuật duyệt theo thứ tự cấp độ cho cây tìm kiếm nhị phân.

Giả sử chúng ta có một cây như thế này -

Trình tự duyệt sẽ như sau:10, 5, 16, 8, 15, 20, 23

Thuật toán

levelOrderTraverse(root):
Begin
   define queue que to store nodes
   insert root into the que.
   while que is not empty, do
      item := item present at front position of queue
      print the value of item
      if left of the item is not null, then
         insert left of item into que
      end if
      if right of the item is not null, then
         insert right of item into que
      end if
      delete front element from que
   done
End

Ví dụ

#include<iostream>
#include<queue>
using namespace std;
class node{
   public:
      int h_left, h_right, bf, value;
      node *left, *right;
};
class tree{
   private:
      node *get_node(int key);
   public:
      node *root;
      tree(){
         root = NULL; //set root as NULL at the beginning
      }
      void levelorder_traversal(node *r);
      node *insert_node(node *root, int key);
};
node *tree::get_node(int key){
   node *new_node;
   new_node = new node; //create a new node dynamically
   new_node->h_left = 0; new_node->h_right = 0;
   new_node->bf = 0;
   new_node->value = key; //store the value from given key
   new_node->left = NULL; new_node->right = NULL;
   return new_node;
}
void tree::levelorder_traversal(node *root){
   queue <node*> que;
   node *item;
   que.push(root); //insert the root at first
   while(!que.empty()){
      item = que.front(); //get the element from the front end
      cout << item->value << " ";
      if(item->left != NULL) //When left child is present, insert into queue
         que.push(item->left);
      if(item->right != NULL) //When right child is present, insert into queue
         que.push(item->right);
      que.pop(); //remove the item from queue
   }
}
node *tree::insert_node(node *root, int key){
   if(root == NULL){
      return (get_node(key)); //when tree is empty, create a node as root
   }
   if(key < root->value){ //when key is smaller than root value, go to the left
      root->left = insert_node(root->left, key);
   } else if(key > root->value) { //when key is greater than root value, go to the right
      root->right = insert_node(root->right, key);
   }
   return root; //when key is already present, do not insert it again
}
main(){
   node *root;
   tree my_tree;
   //Insert some keys into the tree.
   my_tree.root = my_tree.insert_node(my_tree.root, 10);
   my_tree.root = my_tree.insert_node(my_tree.root, 5);
   my_tree.root = my_tree.insert_node(my_tree.root, 16);
   my_tree.root = my_tree.insert_node(my_tree.root, 20);
   my_tree.root = my_tree.insert_node(my_tree.root, 15);
   my_tree.root = my_tree.insert_node(my_tree.root, 8);
   my_tree.root = my_tree.insert_node(my_tree.root, 23);
   cout << "Level-Order Traversal: ";
   my_tree.levelorder_traversal(my_tree.root);
}

Đầu ra

Level-Order Traversal: 10 5 16 8 15 20 23