2020-01-21

Author: JiayangWu

0102.二叉树的层次遍历/0102-二叉树的层次遍历.py

@@ -11,18 +11,18 @@ def levelOrder(self, root):
         :type root: TreeNode
         :rtype: List[List[int]]
         """
-        queue = [root]
+        if not root:
+            return []
+        from collections import deque
+        queue = deque([root])
         res = []
         while queue:
-            next_queue = []
             layer = []
-            for node in queue:
-                if node:
-                    layer.append(node.val)
-                    next_queue += [node.left, node.right]
-            queue = next_queue[:]
-            if layer:
-                res.append(layer[:])
-        return res
-                              
-        
+            for _ in range(len(queue)):
+                cur = queue.popleft()
+                if cur:
+                    layer.append(cur.val)
+                    queue += [cur.left, cur.right]
+            res.append(layer)
+        return res[:-1]
+                

0951.翻转等价二叉树/0951-翻转等价二叉树.py

@@ -0,0 +1,21 @@
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+    def flipEquiv(self, root1, root2):
+        """
+        :type root1: TreeNode
+        :type root2: TreeNode
+        :rtype: bool
+        """
+        if not root1:
+            return root2 is None
+        if not root2:
+            return root1 is None
+        if root1.val != root2.val:
+            return False
+        return (self.flipEquiv(root1.left, root2.left) and self.flipEquiv(root1.right, root2.right)) or (self.flipEquiv(root1.left, root2.right) and self.flipEquiv(root1.right, root2.left))