Characters can be encoded via different numbers. A -> 1, B -> 2, ..., Z -> 26
. Given a string s
of numbers, return the number of possible decodings. For example 12
can be decoded as A,B
and as L
.
Given two lists of a preorder
and inorder
, create a tree and return the root
node.
null
values for the places where the tree does not contain nodes, we could simply iterate over this list and reconstruct the tree from there. But since the null
values are missing, we also need to take a look at the inorder
list.
Given the root
node of a tree, validate whether it is a valid Binary Search Tree. This is a tree where each node is unique, left children are smaller than the root and right children are greater than the root.
Given a string s
, return a list
containing of all possible partitions of that string that are palindromes. A palindrome is a string that is the same backwards as forwards. For example, abba
is a palindrome.
The string aab
can be partitioned as follows: [['a','a','b'], ['aa','b']]
. This is because a single character is by definition a palindrome.
Given the head
of a linked list, remove all items with val
. Afterwards, return the new head.