feat: ✨ add solution, tests and docs for challenge 21

Author: francisco-solis99

adventJs-2023/challenges/challenge21/README.md

@@ -0,0 +1,26 @@
+# Challenge 21 - Binary message 🪐
+
+The elves are receiving strange binary messages from Mars 🪐. Are the aliens trying to communicate with them? 👽
+
+The message that arrives is an array of 0s and 1s. It seems they have found a pattern… To make sure, they want to find the longest segment of the string where the number of 0s and 1s is equal.
+
+## Example
+```ts
+findBalancedSegment([1, 1, 0, 1, 1, 0, 1, 1])
+//                         |________|
+// position of segment:    [2, 5]
+// longest balanced
+// of 0s and 1s
+
+findBalancedSegment([1, 1, 0])
+//                      |__|
+//                     [1, 2]
+
+findBalancedSegment([1, 1, 1])
+// no balanced segments: []
+```
+
+## Notes:
+Keep in mind that if there is more than one balanced pattern, you should return the longest and the first one you find from left to right.
+
+They say that if they find the pattern, they will be able to send a message back to Mars 🚀. It seems that they have to send it to https://mars.codes.

adventJs-2023/challenges/challenge21/challenge21.test.js

@@ -0,0 +1,77 @@
+import { test, describe, expect, expectTypeOf } from 'vitest'
+import { findBalancedSegment } from './challenge21'
+
+describe('Binary message', () => {
+  test('Test 1', () => {
+    expectTypeOf(findBalancedSegment).returns.toEqualTypeOf([])
+  })
+
+  test('Test 2', () => {
+    const received = findBalancedSegment([1, 1, 0, 1, 1, 0, 1, 1])
+    const expected = [
+      2,
+      5
+    ]
+    expect(received).toEqual(expected)
+  })
+
+  test('Test 3', () => {
+    const received = findBalancedSegment([1, 1, 0])
+    const expected = [
+      1,
+      2
+    ]
+    expect(received).toEqual(expected)
+  })
+
+  test('Test 4', () => {
+    const received = findBalancedSegment([1, 1, 1])
+    const expected = []
+    expect(received).toEqual(expected)
+  })
+
+  test('Test 5', () => {
+    const received = findBalancedSegment([1, 0, 1])
+    const expected = [
+      0,
+      1
+    ]
+    expect(received).toEqual(expected)
+  })
+
+  test('Test 6', () => {
+    const received = findBalancedSegment([1, 0, 1, 0])
+    const expected = [
+      0,
+      3
+    ]
+    expect(received).toEqual(expected)
+  })
+
+  test('Test 7', () => {
+    const received = findBalancedSegment([1, 1, 0, 1, 0, 1])
+    const expected = [
+      1,
+      4
+    ]
+    expect(received).toEqual(expected)
+  })
+
+  test('Test 8', () => {
+    const received = findBalancedSegment([1, 0, 0, 0, 1, 1, 1, 0, 0, 0])
+    const expected = [
+      0,
+      7
+    ]
+    expect(received).toEqual(expected)
+  })
+
+  test('Test 6', () => {
+    const received = findBalancedSegment([0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 0, 1])
+    const expected = [
+      5,
+      10
+    ]
+    expect(received).toEqual(expected)
+  })
+})

adventJs-2023/challenges/challenge21/challenge21.ts

@@ -0,0 +1,17 @@
+export function findBalancedSegment (message: number[]): number[] {
+  let range: number = 0
+  let minIndex: number = -1
+
+  for (let i = 0; i < message.length; i += 1) {
+    let count0: number = 0; let count1: number = 0
+    for (let j = i; j < message.length; j += 1) {
+      message[j] === 0 ? count0 += 1 : count1 += 1
+      if ((count1 === count0) && ((j - i) > range)) {
+        range = j - i
+        minIndex = i
+      }
+    }
+  }
+
+  return minIndex < 0 ? [] : [minIndex, range + minIndex]
+}