How to solve this problem asked in Uber OA :-

You can assume N walls with distinct heights.

You are given an array A. A[i] denotes how many walls can be viewed if you stand after the i'th wall

Example array of walls :- [5 4 2 3 1]

A[1] = 1 A[2] = 2 A[3] = 3 A[4] = 3 (You can view 5 , 4 , 3 -> if you stand after 3 and observe.) A[5] = 4

Given an array A ; find the count of permutations possible of size "N" ("N" walls with distinct heights from 1 to N)

Input :- A : [1 2 3 1 2]

Output :- 4

[4 3 2 5 1]

[4 3 1 5 2]

[4 2 1 5 3]

[3 2 1 5 4]

Tried many ways couldn't find any that works.