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1161. Maximum Level Sum of a Binary Tree (Medium)

Given the root of a binary tree, the level of its root is 1, the level of its children is 2, and so on.

Return the smallest level x such that the sum of all the values of nodes at level x is maximal.

 

Example 1:

Input: root = [1,7,0,7,-8,null,null]
Output: 2
Explanation: 
Level 1 sum = 1.
Level 2 sum = 7 + 0 = 7.
Level 3 sum = 7 + -8 = -1.
So we return the level with the maximum sum which is level 2.

Example 2:

Input: root = [989,null,10250,98693,-89388,null,null,null,-32127]
Output: 2

 

Constraints:

  • The number of nodes in the tree is in the range [1, 104].
  • -105 <= Node.val <= 105

Related Topics

[Tree] [Breadth-First Search] [Binary Tree]

Hints

Hint 1 Calculate the sum for each level then find the level with the maximum sum.
Hint 2 How can you traverse the tree ?
Hint 3 How can you sum up the values for every level ?
Hint 4 Use DFS or BFS to traverse the tree keeping the level of each node, and sum up those values with a map or a frequency array.