Create reverse-odd-levels-of-binary-tree.py

Author: kamyu104

Python/reverse-odd-levels-of-binary-tree.py

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+# Time:  O(n)
+# Space: O(n)
+
+# Definition for a binary tree node.
+class TreeNode(object):
+    def __init__(self, val=0, left=None, right=None):
+        pass
+
+
+# bfs
+class Solution(object):
+    def reverseOddLevels(self, root):
+        """
+        :type root: Optional[TreeNode]
+        :rtype: Optional[TreeNode]
+        """
+        q = [root]
+        parity = 0
+        while q:
+            if parity:
+                left, right = 0, len(q)-1
+                while left < right:
+                    q[left].val, q[right].val = q[right].val, q[left].val
+                    left += 1
+                    right -= 1
+            if not q[0].left:
+                break
+            new_q = []
+            for node in q:
+                new_q.append(node.left)
+                new_q.append(node.right)
+            q = new_q       
+            parity ^= 1
+        return root