I have a problem which is shown here. Can someone please suggest an approach for this problem? I looked up the editorial and it said we were supposed to create a tree for each range and treat it as a node.I am not able to understand this concept and the process of tree conversion.Thanking in advance for the help! The details of the question:
A sequence is called a correct parenthesis sequence if it's the following form:
Empty sequence is considered a correct parenthesis sequence.
(A) is considered a correct parenthesis sequence.
XY is considered a correct parenthesis sequence, if both X and Y are correct parenthesis sequences.
A sequence is called a strong parenthesis sequence only if it on form (A), where A is a correct parenthesis sequence.
You have to calculate a weird sum: take [i1, j1] and [i2, j2] every two subarrays of A. The subarrays must not intersect (i.e. i1 ≤ i2 and j1 ≤ i2) and must be strong parenthesis sequences. Then, we add to the sum the minimum length of a subarray, such as it is also a strong parenthesis sequence and it contains both [i1, j1] and [i2, j2] (i.e. if a subsequence of minimum length is [i3, j3], then [i3, j3] is a strong parenthesis sequence and also i3 ≤ i1 ≤ j1 ≤ j3 and i3 ≤ i2 ≤ j2 ≤ j3).
P.S. i am not able to understand the concept of tree converion for ranges and how would LCA help in this context.Thank you.
