upload on 3/11

Author: gyb1325

100. Same Tree.py

@@ -0,0 +1,14 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+
+class Solution:
+
+    def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
+        if p and q:
+            return p.val == q.val and self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)
+        return p is q

101. Symmetric Tree.py

@@ -0,0 +1,22 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+
+class Solution:
+
+    def isSymmetric(self, root: TreeNode) -> bool:
+        if not root:
+            return True
+        return self.helper(root.left, root.right)
+
+    def helper(self, left, right):
+        if not left and not right:
+            return True
+        elif left and right:
+            return left.val == right.val and self.helper(left.left, right.right) and self.helper(left.right, right.left)
+        else:
+            return False

102. Binary Tree Level Order Traversal.py

@@ -0,0 +1,27 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+
+class Solution:
+
+    def levelOrder(self, root: TreeNode) -> List[List[int]]:
+        if not root:
+            return []
+        q = collections.deque()
+        q.append((root, 0))
+        res = []
+        while q:
+            temp, level = q.popleft()
+            if len(res) - 1 == level:
+                res[level].append(temp.val)
+            else:
+                res.append([temp.val])
+            if temp.left:
+                q.append((temp.left, level + 1))
+            if temp.right:
+                q.append((temp.right, level + 1))
+        return res

103. Binary Tree Zigzag Level Order Traversal.py

@@ -0,0 +1,33 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+
+class Solution:
+
+    def zigzagLevelOrder(self, root: TreeNode) -> List[List[int]]:
+        if not root:
+            return []
+        res = []
+        q = collections.deque()
+        q.append((root, 0))
+        while q:
+            temp, level = q.popleft()
+            if level % 2 == 0:
+                if len(res) - 1 == level:
+                    res[level].insert(0, temp.val)
+                else:
+                    res.append([temp.val])
+            else:
+                if len(res) - 1 == level:
+                    res[level].append(temp.val)
+                else:
+                    res.append([temp.val])
+            if temp.right:
+                q.append((temp.right, level + 1))
+            if temp.left:
+                q.append((temp.left, level + 1))
+        return res

104. Maximum Depth of Binary Tree.py

@@ -0,0 +1,14 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+
+class Solution:
+
+    def maxDepth(self, root: TreeNode) -> int:
+        if not root:
+            return 0
+        return max(self.maxDepth(root.left) + 1, self.maxDepth(root.right) + 1)