Given the head of a linked list, remove all items with val. Afterwards, return the new head.
Given an array nums, delete all items that are equal to val. Return the total number of remaining items and perform the deletion in place.
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:
--> 3
/ \
9 5 <--
/ \
--> 7 8
Returns: [[3], [5,9], [7,8]]
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 don’t need to check for a valid solution.