Given a binary tree, find its level order traversal.
Level order traversal of a tree is breadth-first traversal for the tree.
Example 1:
Input:
1
/ \
3 2
Output:1 3 2
Example 2:
Input:
10
/ \
20 30
/ \
40 60
Output:10 20 30 40 60
Your Task:
You don't have to take any input. Complete the function levelOrder() that takes the root node as input parameter and returns a list of integers containing the level order traversal of the given Binary Tree.
Expected Time Complexity: O(n)
Expected Auxiliary Space: O(n)
Constraints:
1 ≤ Number of nodes ≤ 105
1 ≤ Data of a node ≤ 105

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