SDE - 2

Given an array ‘ARR’ and an integer ‘K’, your task is to find all the count of all sub-arrays whose sum is divisible by the given integer ‘K’.

Note:

If there exists no subarray in the given sequence whose sum is divisible by ‘K’ then simply return ‘0’.

Example:

Suppose the given array is ‘ARR’ = { 5, 0, 2, 3, 1} and ‘K = 5’.
As we can see in below image, there are a total of 6 subarrays that have the total sum divisible by ‘K’
So we return the integer 6.

Implement a Trie Data Structure which supports the following three operations:

Operation 1 - insert(word) - To insert a string WORD in the Trie.

Operation 2-  search(word) - To check if a string WORD is present in Trie or not.

Operation 3-  startsWith(word) - To check if there is a string that has the prefix WORD.

Trie is a data structure that is like a tree data structure in its organisation. It consists of nodes that store letters or alphabets of words, which can be added, retrieved, and deleted from the trie in a very efficient way.

In other words, Trie is an information retrieval data structure, which can beat naive data structures like Hashmap, Tree, etc in the time complexities of its operations.

The above figure is the representation of a Trie. New words that are added are inserted as the children of the root node. 

Alphabets are added in the top to bottom fashion in parent to children hierarchy. Alphabets that are highlighted with blue circles are the end nodes that mark the ending of a word in the Trie.

For Example:-

Type = ["insert", "search"], Query = ["coding", "coding].
We return ["null", "true"] as coding is present in the trie after 1st operation.

You have been given an unsorted array ‘ARR’.

Your task is to sort the array in such a way that the array looks like a wave array.

Example:

If the given sequence ‘ARR’ has ‘N’ elements then the sorted wave array looks like - 
‘ARR[0] >= ARR[1]’ and ‘ARR[1] <= ARR[2]’
‘ARR[2] >= ARR[3]’ and ‘ARR[3] <= ARR[4]’
‘ARR[4] >= ARR[5]’ and ‘ARR[5] <= ARR[6]’  And so on.

Note:

1. ‘ARR[0]’ must be greater than or equal to ‘ARR[1]’.

2. There can be multiple arrays that look like a wave array but you have to return only one.

3. We have an internal function that will check your solution and return 'True' in case your array is one of the solutions otherwise return 'False'.

Explanation

The given array ‘ ARR = { 4, 3, 5, 2, 3, 1, 2 } ’
The below figure is a visual representation of the given ‘ARR’ and you can see we can express ‘ARR’ in a waveform array because 
4>3 and 3<5 
5>2 and 2<3
3>1 and 1<2
And it follows the condition of wave array.

Follow up:

Try to solve this problem in linear time complexity.

You are given an Integer ‘N’ you have to convert the integer to words.

For example you are given integer N = 2234 then you have to return the string “two thousand two hundred and thirty four”.

How does Facebook store comments?
Draw LLD for this.