[Hacker Rank] Interview Preparation Kit: Dictionaries and Hashmaps: Sherlock and Anagrams. Solution notes added.

Author: Gonzalo Diaz

docs/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/sherlock_and_anagrams-solution-notes.md

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+# [Sherlock and Anagrams](https://www.hackerrank.com/challenges/sherlock-and-anagrams)
+
+- Difficulty:  `#medium`
+- Category: `#ProblemSolvingMedium` `#DictionariesAndHashmaps` `#Strings`
+
+## About solution
+
+To answer the question of "how many pairs" of words can be anagrammed
+using fragments from adjacent letters of an initial word, two steps are needed:
+
+1) Obtain all possible fragment candidates to be anagrams,
+  from each of the possible fragments that can be generated
+  from adjacent letters of a word.
+
+2) For each list of candidate anagrams,
+  calculate all possible permutations and add them up.
+  The total gives the answer.
+
+The second part of this problem can be solved with the binomial coefficient formula:
+
+<https://en.wikipedia.org/wiki/Binomial_coefficient>
+
+But the entire cost of this formula falls on the "factorial" function.
+
+In javascript, the factorial quickly reaches results that return large numbers,
+in scientific notation, losing precision.
+This loss of precision can result in an erroneous result
+in the final calculation of permutations.
+
+To avoid this problem, it is necessary to introduce large number handling using BigInt.

src/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/sherlock_and_anagrams.ts

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 /**
  * @link Problem definition [[docs/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/sherlock_and_anagrams.md]]
+ * @see Solution Notes: [[docs/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/sherlock_and_anagrams-solution-notes.md]]
  */
 
 import { logger as console } from '../../../logger';