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:
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 don’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.