Traverse a tree where the root
node is given with a zig-zag level and return the values in a list
with one entry per level. For example:
Given the root
node of a binary tree, print all values in order, meaning from left to right on the same level.
To solve this, we can use the standard breadth-first-search (BFS) algorithm in an iterative fashion with a queue
. As an output we use a list
and leverage the position -1
to add the current level to the list. For every level we append one new element to the end of the list.
Given a Sudoku field as a two-dimension list, determine if the field is valid. A valid field only has the number 1-9 once in each sub-field, each row, and each column. The field is not completely filled and we donâ€™t need to check for a valid solution.
Given a list nums
and a positive integer k
, return the top k
frequent items from the list. A time complexity constraint is not given for this task.
Given an array n
of integers, find one peak in O(log*n)
time. A peak is defined as a number where the two numbers immediately left and right are strictly less than the number. Numbers outside of the bounds of this array are considered to be smaller.