Update readme.md

Author: sushant097

coding_solutions/DataStructure_related/Tree/BinaryTreeLevelOrderTraversal.py

@@ -0,0 +1,62 @@
+'''
+Given the root of a binary tree, return the level order traversal of its nodes' values. (i.e., from left to right, level by level)
+
+Example:
+Input: root = [3,9,20,null,null,15,7]
+Output: [[3],[9,20],[15,7]]
+'''
+
+
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+
+
+class Solution:
+    def levelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        # Recursive Solution
+        # Time: O(n); Space: O(n)
+        result = []
+        if root is None:
+            return result
+        
+        def traverse(node, level):
+            if node is None:
+                return
+            if len(result) == level:
+                result.append([])
+            
+            result[level].append(node.val)
+            
+            traverse(node.left, level+1)
+            traverse(node.right, level+1)
+        
+        traverse(root, 0)
+        return result
+    
+            
+class Solution:
+    def levelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        # Iterative Solution
+        # Time: O(n); Space: O(n)
+        result = [] # final result
+        if root is None: return result
+        queue = []  # for level order traversal
+        queue.append(root)
+        while(len(queue) > 0):
+            size = len(queue)
+            currLevel = []
+            while(size > 0):
+                size -= 1
+                curr = queue.pop(0)
+                currLevel.append(curr.val)
+                if curr.left is not None:
+                    queue.append(curr.left)
+                if curr.right is not None:
+                    queue.append(curr.right)
+            result.append(currLevel)
+        return result
+       

coding_solutions/DataStructure_related/Tree/Readme.md

@@ -5,5 +5,6 @@
 | 1 | [Maximum Depth of Tree](https://leetcode.com/problems/maximum-depth-of-binary-tree/)| [python3](https://github.com/sushant097/Data-Structure-Algorithms-Collections-Python/blob/master/coding_solutions/DataStructure_related/Tree/MaxDepthTree.py) |
 | 2 | [Check Validity of BST](https://leetcode.com/problems/validate-binary-search-tree/)| [python3](https://github.com/sushant097/Data-Structure-Algorithms-Collections-Python/blob/master/coding_solutions/DataStructure_related/Tree/CheckValidityBST.py) |
 | 2 | [Check Symmetricity of Binary Tree](https://leetcode.com/problems/symmetric-tree/)| [python3](https://github.com/sushant097/Data-Structure-Algorithms-Collections-Python/blob/master/coding_solutions/DataStructure_related/Tree/CheckSymmetryTree.py) |
+| 2 | [Check Symmetricity of Binary Tree](https://leetcode.com/problems/symmetric-tree/)| [python3](https://github.com/sushant097/Data-Structure-Algorithms-Collections-Python/blob/master/coding_solutions/DataStructure_related/Tree/CheckSymmetryTree.py) |