add solution for alternating characters

readme.md

@@ -1,4 +1,4 @@
-## Algorithms (21/ 167)
+## Algorithms (22/ 167)
 
 | Name                                                      | Tags                    | Solution                                                                                                                            |
 | --------------------------------------------------------- | ----------------------- | ----------------------------------------------------------------------------------------------------------------------------------- |
@@ -14,7 +14,7 @@
 | Count Triplets                                            | `Hash Tables`           | [TypeScript](./src/algorithms/hashtables/count-triplets)                                                                            |
 | Frequency Queries                                         | `Hash Tables`           | [TypeScript](./src/algorithms/hashtables/frequency-queries)                                                                         |
 | Making Anagrams                                           | `Strings`               | [TypeScript](./src/algorithms/strings/make-anagram)                                                                                 |
-| Alternating Characters                                    | `Strings`               |                                                                                                                                     |
+| Alternating Characters                                    | `Strings`               | [TypeScript](./src/algorithms/strings/alternating-characters)                                                                       |
 | Sherlock and the Valid String                             | `Strings`               |                                                                                                                                     |
 | Special String Again                                      | `Strings`               |                                                                                                                                     |
 | Common Child                                              | `Strings`               |                                                                                                                                     |

src/algorithms/strings/alternating-characters/alternating-characters.spec.ts

@@ -0,0 +1,23 @@
+import { alternatingCharacters } from './alternating-characters'
+
+describe('Alternating characters', () => {
+  test.each([
+    { input: 'AAABBBAABB', expected: 6 },
+    { input: 'AABBAABB', expected: 4 },
+    { input: 'ABABABAA', expected: 1 },
+    { input: 'AAABBB', expected: 4 },
+  ])(
+    'should return the minimum number of required deletions for $input',
+    ({ input, expected }) => {
+      expect(alternatingCharacters(input)).toEqual(expected)
+    }
+  )
+
+  it('should handle empty strings', () => {
+    expect(alternatingCharacters('')).toEqual(0)
+  })
+
+  it('should handle single-character strings', () => {
+    expect(alternatingCharacters('A')).toEqual(0)
+  })
+})

src/algorithms/strings/alternating-characters/alternating-characters.ts

@@ -0,0 +1,22 @@
+/**
+ * Given a string containing characters and only.
+ * The task is to change it into a string such that there are no matching adjacent characters.
+ * To do this, you are allowed to delete zero or more characters in the string.
+ * Find the minimum number of required deletions.
+ *
+ * E.g
+ * s = AABAAB // => 2 Deletions
+ *
+ */
+
+export function alternatingCharacters(s: string): number {
+  let deletions = 0
+
+  for (let i = 1; i < s.length; i++) {
+    if (s[i] === s[i - 1]) {
+      deletions++
+    }
+  }
+
+  return deletions
+}