Create 2563. Count the Number of Fair Pairs.md

Map and queue

[refactor] change to md format

Create 2873. Maximum Value of an Ordered Triplet I.md

use hint

add memorization method

Update 2874. Maximum Value of an Ordered Triplet II.md

Create 2874. Maximum Value of an Ordered Triplet II.md

Create 2140. Solving Questions With Brainpower.md

add another implementation for greedy

[refactor] change to md format

add comment to HashSet and Intelligent Sequence Building

add comment to DSU

set

[refactor] change to md format