Print Levels of all nodes in a Binary Tree in C++ Programming.

Given the binary tree, the task is to print the level associated with every key stored in a node starting from 1 to n

In the above tree, nodes are −

10 at level 1
3 and 211 at level 2
140, 162, 100 and 146 at level 3

Given the key the program must print the level of that particular key.

Example

Input: 10 3 211 140 162 100 146
Output:
   level of 10 is 1
   Level of 3 is 2
   Level of 211 is 2
   Level of 140 is 3
   Level of 162 is 3
   Level of 100 is 3
   Level of 146 is 3

Algorithm

START
Step 1 -> create a structure of a node as
   struct node
      struct node *left, *right
      int data
   End
Step 2 -> function to create a node
   node* newnode(int data)
   node *temp = new node
   temp->data = data
   temp->left = temp->right= NULL
   return temp
step 3 -> create function for finding levels of a node
   void levels(Node* root)
      IF root=NULL
      Return
   End
   Create STL queue<pair<struct Node*, int> >que
   que.push({root, 1})
   create STL pair<struct Node*, int> par
   Loop While !que.empty()
      par = que.front()
      que.pop()
      print par.first->data and par.second
      IF par.first->left
         que.push({ par.first->left, par.second + 1 })
      END
      IF par.first->right
         que.push({ par.first->right, par.second + 1 })
      End
   End
STOP

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
//structure of a node
struct Node{
   int data;
   struct Node *left, *right;
};
//it will print levels of a tree
void levels(Node* root){
   if (root==NULL)
      return;
   queue<pair<struct Node*, int> >que;
   que.push({root, 1});
   pair<struct Node*, int> par;
   while (!que.empty()) {
      par = que.front();
      que.pop();
      cout << "Level of " << par.first->data << " is " << par.second << "\n";
      if (par.first->left)
         que.push({ par.first->left, par.second + 1 });
      if (par.first->right)
         que.push({ par.first->right, par.second + 1 });
   }
}
//function to create nodes annd hence generate tree
Node* newnode(int data){
   Node* temp = new Node;
   temp->data = data;
   temp->left = temp->right = NULL;
   return temp;
}
int main(){
   Node* root = NULL;
   //it will create a node
   root = newnode(34);
   root->left = newnode(12);
   root->right = newnode(50);
   root->left->left = newnode(11);
   root->left->right = newnode(54);
   levels(root);
   return 0;
}

Output

if we run the above program then it will generate the following output

Level of 34 is 1
Level of 12 is 2
Level of 50 is 2
Level of 11 is 3
Level of 54 is 3