In level order traversing we visit the each node of tree level by level.
let's say we have a tree as you see in the image given below.

here in the tree, there are 4 levels. so to find the level order of this tree we visit each level from top to bottom and left to right and traverse each node at that level.
First, we visit the level 0 of the tree. so the level order of tree is P
Now come to level 1. and in level 1 there are two node A and X so the level order of tree become
P A X
then we visit level 2 so the new level order of tree is
P A X T Z M G
then we visit level 3 so the new level order of tree is
P A X T Z M G Y L F C
so this is the complete level order of the given tree.
let's say we have a tree as you see in the image given below.

here in the tree, there are 4 levels. so to find the level order of this tree we visit each level from top to bottom and left to right and traverse each node at that level.
First, we visit the level 0 of the tree. so the level order of tree is P
Now come to level 1. and in level 1 there are two node A and X so the level order of tree become
P A X
then we visit level 2 so the new level order of tree is
P A X T Z M G
then we visit level 3 so the new level order of tree is
P A X T Z M G Y L F C
so this is the complete level order of the given tree.
Program to find the level order of tree using python programming.
from collections import deque class Node: def __init__(self, value): self.info = value self.lchild = None self.rchild = None class BinaryTree: def __init__(self): self.root = None def is_empty(self): return self.root is None def display(self): self._display(self.root, 0) print() def _display(self,p,level): if p is None: return self._display(p.rchild, level+1) print() for i in range(level): print(" ", end='') print(p.info) self._display(p.lchild, level+1) def preorder(self): self._preorder(self.root) print() def _preorder(self,p): if p is None: return print(p.info, " ", end='') self._preorder(p.lchild) self._preorder(p.rchild) def inorder(self): self._inorder(self.root) print() def _inorder(self,p): if p is None: return self._inorder(p.lchild) print(p.info," ", end='') self._inorder(p.rchild) def postorder(self): self._postorder(self.root) print() def _postorder(self,p): if p is None: return self._postorder(p.lchild) self._postorder(p.rchild) print(p.info," ",end='') def level_order(self): if self.root is None: print("Tree is empty") return qu = deque() qu.append(self.root) while len(qu) != 0: p = qu.popleft() print(p.info + " ", end='') if p.lchild is not None: qu.append(p.lchild) if p.rchild is not None: qu.append(p.rchild) def height(self): return self._height(self.root) def _height(self,p): if p is None: return 0 hL = self._height(p.lchild) hR = self._height(p.rchild) if hL > hR: return 1 + hL else: return 1 + hR def create_tree(self): self.root = Node('p') self.root.lchild = Node('Q') self.root.rchild = Node('R') self.root.lchild.lchild = Node('A') self.root.lchild.rchild = Node('B') self.root.rchild.lchild = Node('X') ########################## bt = BinaryTree() bt.create_tree() bt.display() print() print("Preorder : ") bt.preorder() print("") print("Inorder : ") bt.inorder() print() print("Postorder : ") bt.postorder() print() print("Level order : ") bt.level_order() print() print("Height of tree is ", bt.height())
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