feat: solve advent of code 2015 day 1

Author: JCPedroza

src/advent-of-code/2015/01-not-quite-lisp/README.md

@@ -0,0 +1,61 @@
+# Advent of Code 2015 Day 1 - Not Quite Lisp
+
+## Part A
+
+Santa is trying to deliver presents in a large apartment building, but he can't
+find the right floor - the directions he got are a little confusing. He starts
+on the ground floor (floor `0`) and then follows the instructions one character
+at a time.
+
+An opening parenthesis, `(`, means he should go up one floor, and a closing
+parenthesis, `)`, means he should go down one floor.
+
+The apartment building is very tall, and the basement is very deep; he will
+never find the top or bottom floors.
+
+To what floor do the instructions take Santa? Assume that the input string can
+only contain the characters `(`, `)`.
+
+### Expected Behavior
+
+```
+In: ''
+Out: 0
+
+In: '(())'
+Out: 0
+
+In: '(((('
+Out: 4
+
+In: '))))'
+Out: -4
+
+In: ')())())'
+Out: -3
+```
+
+## Part B
+
+Now, given the same instructions, find the position of the first character that
+causes him to enter the basement (floor -1). The first character in the
+instructions has position 1, the second character has position 2, and so on.
+
+What is the position of the character that causes Santa to first enter the
+basement? Throw an error if the basement is never reached.
+
+### Expected Behavior
+
+```
+In: ''
+Out: Throw error
+
+In: ')'
+Out: 1
+
+In: '())()'
+Out: 3
+
+In: '()((()'
+Out: Throw error
+```

src/advent-of-code/2015/01-not-quite-lisp/part-a/nqla-for-loop.js renamed to src/advent-of-code/2015/01-not-quite-lisp/part-a/nqla-loop-for.js

@@ -2,16 +2,18 @@
  * Finds the floor where santa needs to deliver presents. Uses tail recursion.
  *
  * Time complexity: O(n)
- * Space complexity: O(n)
+ * Space complexity: O(n) (call stack size)
  *
  * @param {string} dir Floor directions.
  * @returns {number} Floor number.
  */
 const findFloor = (dir) => {
   /**
    * Recursive helper function.
+   *
    * @param {number} idx Current index.
    * @param {number} sum Current sum.
+   * @returns {number} Floor number.
    */
   const recur = (idx, sum) => {
     if (idx >= dir.length) return sum

src/advent-of-code/2015/01-not-quite-lisp/part-a/nqla-recursive-tail.js

@@ -2,7 +2,7 @@
  * Finds the floor where santa needs to deliver presents. Uses recursion.
  *
  * Time complexity: O(n)
- * Space complexity: O(n)
+ * Space complexity: O(n^2) (string copy in each call stack)
  *
  * @param {string} dir Floor directions.
  * @returns {number} Floor number.

src/advent-of-code/2015/01-not-quite-lisp/part-a/nqla-recursive.js

@@ -1,4 +1,4 @@
-const nqlaForLoop = require('./nqla-for-loop')
+const nqlaForLoop = require('./nqla-loop-for')
 const nqlaReduce = require('./nqla-reduce')
 const nqlaRecursive = require('./nqla-recursive')
 const nqlaTail = require('./nqla-recursive-tail')

src/advent-of-code/2015/01-not-quite-lisp/part-a/nqla.repo.js

@@ -11,23 +11,23 @@ const bigInput = readFileSync(bigInputPath, 'utf-8')
 
 for (const { fun, id } of solutions) {
   describe(`Advent of Code 'Not Quite Lisp (part a)' solution '${id}'`, () => {
-    it('Solves empty string', () => {
+    it('solves empty string', () => {
       assert.equal(fun(''), 0)
     })
 
-    it('Solves string of length 1', () => {
+    it('solves string of length 1', () => {
       assert.equal(fun('('), 1)
       assert.equal(fun(')'), -1)
     })
 
-    it('Solves string of length 4', () => {
+    it('solves string of length 4', () => {
       assert.equal(fun('(())'), 0)
       assert.equal(fun('()()'), 0)
       assert.equal(fun('((()'), 2)
       assert.equal(fun('))))'), -4)
     })
 
-    it('Solves big input', () => {
+    it('solves big input', () => {
       assert.equal(fun(bigInput), 232)
     })
   })

src/advent-of-code/2015/01-not-quite-lisp/part-a/nqla.test.js

@@ -8,7 +8,7 @@ const bigInputPath = join(__dirname, '../input-big.txt')
 const bigInput = readFileSync(bigInputPath, 'utf-8')
 
 const args = [bigInput]
-const runs = 1_000
+const runs = 2_000
 const id = 'Advent of Code "Not Quite Lisp (part a)"'
 
 timeAndReport(solutions, args, runs, id)

src/advent-of-code/2015/01-not-quite-lisp/part-a/nqla.time.js

@@ -0,0 +1,27 @@
+/**
+ * Finds the position of the first character that causes santa to enter the
+ * basement (floor -1). Uses a for loop.
+ *
+ * Time complexity: O(n)
+ * Space complexity: O(1)
+ *
+ * @param {string} dir Floor directions.
+ * @returns {number} Position of first character that reaches the basement.
+ */
+const findBasePos = (dir) => {
+  let floor = 0
+
+  for (let idx = 0; idx < dir.length; idx++) {
+    if (dir[idx] === '(') floor++
+    else floor--
+
+    if (floor === -1) return idx + 1
+  }
+
+  throw new Error('Basement was never reached')
+}
+
+module.exports = {
+  fun: findBasePos,
+  id: 'for-loop'
+}

src/advent-of-code/2015/01-not-quite-lisp/part-b/nqlb-loop-for.js

@@ -0,0 +1,30 @@
+/**
+ * Finds the position of the first character that causes santa to enter the
+ * basement (floor -1). Uses a while loop.
+ *
+ * Time complexity: O(n)
+ * Space complexity: O(1)
+ *
+ * @param {string} dir Floor directions.
+ * @returns {number} Position of first character that reaches the basement.
+ */
+const findBasePos = (dir) => {
+  let floor = 0
+  let idx = 0
+
+  while (idx < dir.length) {
+    if (dir[idx] === '(') floor++
+    else floor--
+
+    if (floor === -1) return idx + 1
+
+    idx++
+  }
+
+  throw new Error('Basement was never reached')
+}
+
+module.exports = {
+  fun: findBasePos,
+  id: 'while-loop'
+}

src/advent-of-code/2015/01-not-quite-lisp/part-b/nqlb-loop-while.js

@@ -0,0 +1,33 @@
+/**
+ * Finds the position of the first character that causes santa to enter the
+ * basement (floor -1). Uses tail recursion.
+ *
+ * Time complexity: O(n)
+ * Space complexity: O(n) (call stack size)
+ *
+ * @param {string} dir Floor directions.
+ * @returns {number} Position of first character that reaches the basement.
+ */
+const findBasePos = (dir) => {
+  /**
+   * Recursive helper function.
+   *
+   * @param {number} idx Current index.
+   * @param {number} sum Current sum.
+   * @returns {number} Position of first character that reaches the basement.
+   */
+  const recur = (idx, sum) => {
+    if (sum === -1) return idx
+    if (idx >= dir.length) throw new Error('Basement was never reached')
+
+    if (dir[idx] === '(') return recur(idx + 1, sum + 1)
+    else return recur(idx + 1, sum - 1)
+  }
+
+  return recur(0, 0)
+}
+
+module.exports = {
+  fun: findBasePos,
+  id: 'tail-recursion'
+}

src/advent-of-code/2015/01-not-quite-lisp/part-b/nqlb-recursive-tail.js

@@ -0,0 +1,11 @@
+const nqlbWhileLoop = require('./nqlb-loop-while')
+const nqlbForLoop = require('./nqlb-loop-for')
+const nqlbTailRecursion = require('./nqlb-recursive-tail')
+
+const solutions = [
+  nqlbWhileLoop,
+  nqlbForLoop,
+  nqlbTailRecursion
+]
+
+module.exports = solutions

src/advent-of-code/2015/01-not-quite-lisp/part-b/nqlb.repo.js

@@ -0,0 +1,30 @@
+const { describe, it } = require('node:test')
+const assert = require('node:assert/strict')
+
+const { readFileSync } = require('fs')
+const { join } = require('path')
+
+const solutions = require('./nqlb.repo')
+
+const bigInputPath = join(__dirname, '../input-big.txt')
+const bigInput = readFileSync(bigInputPath, 'utf-8')
+
+for (const { fun, id } of solutions) {
+  describe(`Advent of Code 'Not Quite Lisp (part b)' solution '${id}'`, () => {
+    it('throws error for empty string', () => {
+      assert.throws(() => fun(''))
+    })
+
+    it('solves string of length 1', () => {
+      assert.equal(fun(')'), 1)
+    })
+
+    it('solves big input', () => {
+      assert.equal(fun(bigInput), 1783)
+    })
+
+    it('throws error if basement is not reached', () => {
+      assert.throws(() => fun('()((()'))
+    })
+  })
+}

src/advent-of-code/2015/01-not-quite-lisp/part-b/nqlb.test.js

@@ -0,0 +1,14 @@
+const { readFileSync } = require('fs')
+const { join } = require('path')
+
+const solutions = require('./nqlb.repo')
+const { timeAndReport } = require('../../../../../lib/time')
+
+const bigInputPath = join(__dirname, '../input-big.txt')
+const bigInput = readFileSync(bigInputPath, 'utf-8')
+
+const args = [bigInput]
+const runs = 10_000
+const id = 'Advent of Code "Not Quite Lisp (part b)"'
+
+timeAndReport(solutions, args, runs, id)