Completed BFS-1

Problem_1.py

@@ -0,0 +1,56 @@
+# 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
+from collections import deque
+
+
+class Solution:
+    def levelOrder(self, root):
+        result = []
+        if not root:
+            return result
+        q = deque()
+        q.append(root)
+        while q:
+            qSize = len(q)
+            temp = []
+            for i in range(qSize):
+                front = q.popleft()
+                temp.append(front.val)
+                if front.left:
+                    q.append(front.left)
+                if front.right:
+                    q.append(front.right)
+            result.append(list(temp))
+        return result
+
+
+'''
+DFS Code
+
+# 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]]:
+        self.result = []
+        self.dfs(root, 0)
+        return self.result
+
+    def dfs(self, root, level):
+        if not root:
+            return
+        if level >= len(self.result):
+            self.result.append([root.val])
+        else:
+            self.result[level].append(root.val)
+        self.dfs(root.left, level + 1)
+        self.dfs(root.right, level + 1)
+
+'''

Problem_2.py

@@ -0,0 +1,28 @@
+from collections import deque
+
+
+class Solution:
+    def canFinish(self, numCourses, prerequisites):
+        adj = [[] for _ in range(numCourses)]
+        indegree = [0] * numCourses
+        for a, b in prerequisites:
+            adj[b].append(a)
+            indegree[a] += 1
+
+        q = deque()
+        courseRemain = numCourses
+
+        for idx, count in enumerate(indegree):
+            if count == 0:
+                q.append(idx)
+
+        while q:
+            front = q.popleft()
+            courseRemain -= 1
+            if courseRemain == 0:
+                return True
+            for node in adj[front]:
+                indegree[node] -= 1
+                if indegree[node] == 0:
+                    q.append(node)
+        return False