Completed BFS-1

Problem1.py

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+#Problem 102. BINARY TREE LEVEL ORDER TRAVERSAL
+# TIME COMPELXITY: O(N) where N denotes the nodes that are present in a given tree structure
+# SPACE COMPLEXITY: O(N) since we will be needing to store the nodes that are coming from these level order traversal 
+
+
+
+# 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]]:
+        if not root:
+            return []
+        result=[]
+        q=deque([root])
+        while q:
+            size=len(q)
+            level=[]
+            for i in range(size):
+                node=q.popleft()
+                level.append(node.val)
+                if node.left:
+                    q.append(node.left)
+                if node.right:
+                    q.append(node.right)
+            result.append(level)
+        return result
+
+

Problem2.py

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+#Problem 207. COURSE SCHEDULE
+# TIME COMPELXITY: O(V+E) where V is the numberCourses and E is the prerequisites
+# SPACE COMPLEXITY: O(V+E) to store the graph, queue and indegree array.
+
+class Solution:
+    def canFinish(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
+        indegree=[0]*numCourses
+        graph={}
+
+        for prerequisite in prerequisites:
+            indegree[prerequisite[0]]+=1
+            if prerequisite[1] not in graph:
+                graph[prerequisite[1]]=[]
+            graph[prerequisite[1]].append(prerequisite[0])
+
+        count=0
+        q=deque()
+
+        for i in range(numCourses):
+            if indegree[i]==0:
+                q.append(i)
+                count+=1
+
+        if not q:
+            return False
+        if count==numCourses:
+            return True
+
+        while q:
+            current=q.popleft()
+            dependencies=graph.get(current)
+            if dependencies:
+                for dependencie in dependencies:
+                    indegree[dependencie]-=1
+                    if indegree[dependencie]==0:
+                        q.append(dependencie)
+                        count+=1
+                        if count==numCourses:
+                            return True
+
+        return False