Assistant System Engineer

Ninja is playing with a string ‘S’ consisting of only equal numbers of opening brackets ‘[’ and closing brackets ’]’. The string was initially balanced but due to Ninja’s friend’s mischief, the string got shuffled up. Now, Ninja wants to make the string balanced again using the minimum number of swaps. Can you help Ninja to find the minimum number of swaps required to make the string balanced again?

A string is called balanced if and only if:

1.It is the empty string, or

2.It can be written as AB, where both A and B are balanced strings, or

3.It can be written as [C], where C is a balanced string.

You are given a string ‘S’ having ‘N/2’ opening brackets and N/2 closing brackets. You have to find the minimum number of swaps required to make ‘S’ balanced again.

For Example

If the given string S = “ [[]]][ ”, the answer will be 1 as if we swap the last and second last character, the string will be balanced.

You have been given an integer array/list 'ARR' of size 'N'. Your task is to return the total number of those subsequences of the array in which all the elements are equal.

A subsequence of a given array is an array generated by deleting some elements of the given array with the order of elements in the subsequence remaining the same as the order of elements in the array.

Note :

As this value might be large, print it modulo 10^9 + 7

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