Tree Packed to the Left

Medium

You are given the root of a binary tree. Check whether it is tightly packed: every level except possibly the last is completely filled, and the nodes of the last level sit side by side starting from the far left, with no gaps. Return True if the tree is packed this way and False otherwise.

Example 1

root=tree_node([7, 3, 9, 1, 4]) → True

The first two levels are full, and the two nodes on the last level take the leftmost spots.

Example 2

root=tree_node([7, 3, 9, None, 4]) → False

Node 3 has no left child but has a right one, so the last level has a gap on the left.

Example 3

root=tree_node([7, 3, 9, 1, 4, 2, 8, 5]) → True

Constraints

1 ≤ number of nodes ≤ 100
1 ≤ Node.val ≤ 1000

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Topics

Tree Breadth-First Search Binary Tree

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Input

root=tree_node([7, 3, 9, 1, 4])

Expected

True

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