Binary tree levelwise travalsal added

BST/bst-lvl-order-tvsl.py

@@ -0,0 +1,81 @@
+#Problem name 102. Binary Tree Level Order Traversal
+#https://leetcode.com/problems/binary-tree-level-order-traversal/
+# Complexity 
+#   time ->  O(n)
+#   memory -> O(n)
+"""
+Tree Structure 
+
+                  Root
+                   |
+                  100
+                /      \ 
+               50       180
+              /  \     /    \
+             40   60   150   190
+            /            \      \
+           30             160     200
+
+"""
+
+
+# Definition for a binary tree node.
+import collections
+
+
+#structure of the Tree node
+class TreeNode:
+    def __init__(self, val, left=None, right=None):
+        self.left = left
+        self.right = right
+        self.val = val
+
+
+# Output -> List[List[int]]:
+#Level starts form 0 to .... n
+
+class Solution:
+    def levelOrder(self, root):
+        self.lst=collections.defaultdict(list)
+        def dfs(r, lvl):
+            if not r:
+                return 
+            self.lst[lvl].append(r.val)
+            dfs(r.left, lvl+1)
+            dfs(r.right, lvl+1)
+            return 
+        dfs(root, 0) #DFS approach ot visit the tree in recurssive approach with value and level
+        res =[]
+        for key in sorted(self.lst.keys(), reverse =False):
+            res.append(self.lst[key])
+        return res
+
+
+# intiate nodes of the Tree
+t_root = TreeNode(100)
+node_60 = TreeNode(60)
+node_50 = TreeNode(50)
+node_40 = TreeNode(40)
+node_30 = TreeNode(30)
+node_150 = TreeNode(150)
+node_160 = TreeNode(160)
+node_180 = TreeNode(180)
+node_190 = TreeNode(190)
+node_220 = TreeNode(220)
+
+#Build Tree
+t_root.left = node_50
+t_root.right = node_180
+node_50.left = node_40
+node_40.left = node_30
+node_50.right = node_60
+node_180.left = node_150
+node_180.right = node_190
+node_150.right = node_160
+node_190.right  = node_220
+
+print(t_root.val)
+
+sol = Solution()
+result = sol.levelOrder(t_root)
+print(result)