Power Programmer

A few days back, Ninja encountered a string containing characters from ‘A’ to ‘Z’ which indicated a secret message. For security purposes he encoded each character of the string to its numeric value, that is, A = 1, B = 2, C = 3, till Z = 26 and combined them as a single sequence (SEQ) of digits of length N. Let's say the message was "LA", Ninja encoded it as 121 for L=12 and A=1.

Today, when he read the encoded secret message, he realised that he was not able to decode the original string. So, the Ninja is wondering in how many ways he can decode the numeric sequence to some valid string.

A valid string is a string with characters from A to Z and no other characters.

Example:

Let the encoded sequence be 121,

The first way to decode 121 is:
1 = A
2 = B
1 = A
Thus, the decoded string will be ABA.

The second way to decode 121 is:
12 = L
1 = A
Thus, the decoded string will be LA.

The third way to decode 121 is:
1 = A
21 = U
Thus, the decoded string will be AU.

So, there will be 3 ways to decode the sequence 121 i.e. [(ABA), (LA), (AU)].

Note:

The input sequence will always have at least 1 possible way to decode.    

As the answer can be large, return your answer modulo 10^9  + 7.

Follow Up:

Can you solve this using constant extra space?

You are given two integer arrays ARR1 and ARR2 of length N and M respectively. You have to return true if ARR2 is a subset of ARR1, otherwise, return false.

For Example:

If the given arrays are [1, 2, 3] and [1, 2] then you need to return true as ARR2 is a subset of ARR1, but if the given arrays are [1, 2, 3] and [1, 2, 2] then you need to return false since ARR2 is not a subset of ARR1.

There is a problem set of N problems. It is given that you have A easy problems, B medium problems and C hard problems.
It is given that any valid problemset to be used in the quiz should meet the conditions
given below:
•No two problems with the same difficulty should be adjacent in the final problemset
.There is at least one easy and one hard problem in the final problemset. 
• Number of medium problems is strictly greater than easy problems in the final
problemset 
• Number of medium problems is strictly greater than hard problems in the final problemset.
Your task is count the total number of valid problemset that can be created from the problems provided. Since this number is large you need to print the modulo 10^9 +7.
Note: Two problemset's are considered different if there is some index i where the difficulty of problems in these two sets are different.

For a given input string(str), find and return the total number of words present in it.

It is assumed that two words will have only a single space in between. Also, there wouldn't be any leading and trailing spaces in the given input string.