From bcd060c6d37382f5e6f60a786da7e08474ec5dfd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A4ghib=20Hasan?= <raghibmidhat@gmail.com>
Date: Thu, 25 Apr 2024 16:43:16 +0300
Subject: [PATCH] add solution for sherlock and anagrams

---
 readme.md                                     |  4 +-
 .../sherlock-and-anagrams.spec.ts             | 21 +++++++
 .../sherlock-and-anagrams.ts                  | 61 +++++++++++++++++++
 3 files changed, 84 insertions(+), 2 deletions(-)
 create mode 100644 src/algorithms/hashtables/sherlock-and-anagrams/sherlock-and-anagrams.spec.ts
 create mode 100644 src/algorithms/hashtables/sherlock-and-anagrams/sherlock-and-anagrams.ts

diff --git a/readme.md b/readme.md
index af9940c..12295ab 100644
--- a/readme.md
+++ b/readme.md
@@ -1,4 +1,4 @@
-## Algorithms (16/ 167)
+## Algorithms (17/ 167)
 
 | Name                                                      | Tags                    | Solution                                                                |
 | --------------------------------------------------------- | ----------------------- | ----------------------------------------------------------------------- |
@@ -10,7 +10,7 @@
 | Array Manipulation                                        | `Arrays`                | [TypeScript](./src/algorithms/arrays/array-manipulation)                |
 | Ransom Note                                               | `Hash Tables`           | [TypeScript](./src/algorithms/hashtables/ransom-note)                   |
 | Two Strings                                               | `Hash Tables`           | [TypeScript](./src/algorithms/hashtables/two-strings)                   |
-| Sherlock and Anagrams                                     | `Hash Tables`           |                                                                         |
+| Sherlock and Anagrams                                     | `Hash Tables`           | [TypeScript](./src/algorithms/hashtables/sherlock-and-anagrams)         |
 | Count Triplets                                            | `Hash Tables`           |                                                                         |
 | Frequency Queries                                         | `Hash Tables`           |                                                                         |
 | Making Anagrams                                           | `Strings`               | [TypeScript](./src/algorithms/strings/make-anagram)                     |
diff --git a/src/algorithms/hashtables/sherlock-and-anagrams/sherlock-and-anagrams.spec.ts b/src/algorithms/hashtables/sherlock-and-anagrams/sherlock-and-anagrams.spec.ts
new file mode 100644
index 0000000..1e057c3
--- /dev/null
+++ b/src/algorithms/hashtables/sherlock-and-anagrams/sherlock-and-anagrams.spec.ts
@@ -0,0 +1,21 @@
+import {
+  sherlockAndAnagrams,
+  sherlockAndAnagrams2,
+} from './sherlock-and-anagrams'
+
+describe('Sherlock and Anagrams', () => {
+  it('should return correct number of anagram pairs for "mom"', () => {
+    expect(sherlockAndAnagrams('mom')).toBe(2)
+    expect(sherlockAndAnagrams2('mom')).toBe(2)
+  })
+
+  it('should return the correct number of anagram pairs for "abba"', () => {
+    expect(sherlockAndAnagrams('abba')).toBe(4)
+    expect(sherlockAndAnagrams2('abba')).toBe(4)
+  })
+
+  it('should return 0 for no anagrams', () => {
+    expect(sherlockAndAnagrams('abcd')).toBe(0)
+    expect(sherlockAndAnagrams2('abcd')).toBe(0)
+  })
+})
diff --git a/src/algorithms/hashtables/sherlock-and-anagrams/sherlock-and-anagrams.ts b/src/algorithms/hashtables/sherlock-and-anagrams/sherlock-and-anagrams.ts
new file mode 100644
index 0000000..9fd7bae
--- /dev/null
+++ b/src/algorithms/hashtables/sherlock-and-anagrams/sherlock-and-anagrams.ts
@@ -0,0 +1,61 @@
+/**
+ * Sherlock and Anagrams
+ *
+ * Two strings are anagrams of each other if the letters of one string can be rearranged to form the other string.
+ * Given a string, find the number of pairs of substrings of the string that are anagrams of each other.
+ *
+ * Example:
+ *  s = mom
+ *
+ * The list of all anagrammatic pairs is [m,m], [mo,om] at positions 0 and 1 respectively.
+ *
+ * Constraints
+ *
+ * 1 <= q <= 100  at positions  respectively.
+ *
+ */
+
+export function sherlockAndAnagrams(s: string): number {
+  const substringCounts = new Map<string, number>()
+
+  for (let i = 0; i < s.length; i++) {
+    for (let j = i + 1; j <= s.length; j++) {
+      let curr = [...s.slice(i, j)].sort().join('')
+
+      if (substringCounts.has(curr)) {
+        substringCounts.set(curr, substringCounts.get(curr)! + 1)
+      } else {
+        substringCounts.set(curr, 1)
+      }
+    }
+  }
+
+  return [...substringCounts.values()].reduce(
+    (acc, curr) => acc + (curr * (curr - 1)) / 2,
+    0
+  )
+}
+
+export function sherlockAndAnagrams2(s: string): number {
+  const generateSortedSubstrings = (_: unknown, i: number) =>
+    Array.from({ length: s.length - i }, (_, j) =>
+      s
+        .slice(j, j + i + 1)
+        .split('')
+        .sort()
+        .join('')
+    )
+
+  const sortedSubstringCounts = s
+    .split('')
+    .flatMap(generateSortedSubstrings)
+    .reduce(
+      (map, substr) => map.set(substr, (map.get(substr) || 0) + 1),
+      new Map<string, number>()
+    )
+
+  return [...sortedSubstringCounts.values()].reduce(
+    (acc, count) => acc + (count * (count - 1)) / 2,
+    0
+  )
+}