MERN Stack Developer

You are given an array/list ‘ARR’ containing permutation from 1 to 'N' and an integer ‘K’. You have a binary string ‘S’ of size ‘N’ initialised to all zeroes. You perform ‘N’ operations on 'S' as follows:

In the ‘i-th’ operation, you set the ‘ARR[i]-th’ bit of ‘S’ to ‘1’. 

After performing each operation, you get a "group". A "group" of '1s', is a substring of all '1s' in 'S' which can not be extended to its left or right by adding '1s'.

You have to find the last operation when there was a group of size exactly 'K'. If the group of size 'K' was never present, then return -1.

Note :

Both 'ARR' and 'S' are 1 indexed. 

You are given a string ‘STR’, which represents an expression. Your task is to evaluate the value of the expression. The integer division should truncate toward zero.

For Example:

Consider STR = “3+2*2”
Using the BODMAS rule, the expression after evaluation gives 7. Hence, the answer is 7.

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