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Level_order_traversal.py
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Level_order_traversal.py
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"""
Given a binary tree, find its level order traversal.
Level order traversal of a tree is breadth-first traversal for the tree.
Input:
10
/ \
20 30
/ \
40 60
Output:10 20 30 40 60
Expected Time Complexity: O(n)
Expected Auxiliary Space: O(n)
Constraints:
1 ≤ Number of nodes ≤ 105
1 ≤ Data of a node ≤ 105
"""
# first way
class Solution:
def height(self, root):
if root == None:
return 0
return max(self.height(root.left), self.height(root.right)) + 1
def currentLevel(self, root, level, arr):
if root == None:
return
if level == 1:
arr.append(root.data)
if level > 1:
self.currentLevel(root.left, level - 1, arr)
self.currentLevel(root.right, level - 1, arr)
def levelOrder(self, root):
arr = []
h = self.height(root)
for i in range(1, h + 1, 1):
self.currentLevel(root, i, arr)
1
return arr
# second way
def levelOrder(self, root):
if not root:
return []
q = [] # queue for nodes
q.append(root)
ans = [] # list for data
while len(q) > 0:
ans.append(q[0].data)
temp = q.pop(0)
if temp.left:
q.append(temp.left)
if temp.right:
q.append(temp.right)
return ans