Grokking the Coding Interview: Patterns for Coding Questions
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Reverse Level Order Traversal (easy)

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Anonymous

· 2 years ago

Reverse Level Order Traversal Testcases seems wrong. My code unchanged from Level Order Traversal works.

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A

Anonymous

· 3 years ago

instead of:

result.push_back(currentLevel);

use:

result.insert(result.begin(), currentLevel);

It's a simple change that works. it might incur more moves in the container though.

A

Anonymous

· 3 years ago

In the problem function returns vector<vector<int>> In the solution it returns deque<vector<int>> This is a huge difference. Please update!

A

Anonymous

· 3 years ago

This is a little confusing since you expect that what's in the boiler plate here is suppose to be in the solution

Boiler Plate for Question

class Solution:
  def traverse(self, root):
    deq = deque()
    # TODO: Write your code here

    result = [list(sublist) for sublist in deq]
    return result

Solution - FOLLOWS SIMILAR FORMAT AS 'LEVEL ORDER TRAVERSAL' QUESTION

def traverse(root):
  result = deque()
  if root is None:
    return result

  queue = deque()
  queue.append(root)
  while queue:
    levelSize = len(queue)
    currentLevel = []
    for _ in range(levelSize):
      currentNode = queue.popleft()
      # add the node to the current level
      currentLevel.append(currentNode.val)
      # insert the children of current node in the que
A

Anonymous

· 3 years ago

Instead of LinkedList to hold the level arrays and adding at the beginning of the LinkedList every time, a Stack<List<Integer>> is another option we could try. It worked for me.

A

Anonymous

· 4 years ago

Instead of appending list at the beginning to reverse, why not use Stack instead?

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