Create maximum-level-sum-of-a-binary-tree.py

Author: kamyu104

Python/maximum-level-sum-of-a-binary-tree.py

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+# Time:  O(n)
+# Space: O(h)
+
+import collections
+
+
+# Definition for a binary tree node.
+class TreeNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+
+# dfs solution
+class Solution(object):
+    def maxLevelSum(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        def dfs(node, i, level_sums):
+            if not node:
+                return
+            if i == len(level_sums):
+                level_sums.append(0)
+            level_sums[i] += node.val
+            dfs(node.left, i+1, level_sums)
+            dfs(node.right, i+1, level_sums)
+
+        level_sums = []
+        dfs(root, 0, level_sums)
+        return level_sums.index(max(level_sums))+1
+
+    
+# Time:  O(n)
+# Space: O(w)
+# bfs solution
+class Solution2(object):
+    def maxLevelSum(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        result, level, max_total = 0, 1, float("-inf")
+        q = collections.deque([root])
+        while q:
+            total = 0
+            for _ in xrange(len(q)):
+                node = q.popleft()
+                total += node.val
+                if node.left:
+                    q.append(node.left)
+                if node.right:
+                    q.append(node.right)
+            if total > max_total:
+                result, max_total = level, total
+            level += 1
+        return result