feat(2020-day-11): advance seating configurations

Author: developher-net

2020/day-11/seating.js

@@ -0,0 +1,72 @@
+
+const parse = (data) => {
+  return data.split('\n').map((row) => {
+    return row.split('')
+  })
+}
+
+const format = (seatMap) => {
+  return seatMap.map((row) => row.join('')).join('\n')
+}
+
+const occupiedNearby = ({ x, y, seatMap }) => {
+  let temp = ''
+
+  for (let row = y - 1; row <= y + 1; row++) {
+    for (let col = x - 1; col <= x + 1; col++) {
+      try {
+        temp += seatMap[row][col] || '-'
+      } catch {
+        temp += '-'
+      }
+    }
+    temp += '\n'
+  }
+  const occupied = (temp.match(/#/g) || []).length
+
+  // console.debug(temp)
+  // console.debug(`------${occupied}------------`)
+  return occupied
+}
+
+const advance = (seatMap) => {
+  return seatMap.map((row, y) => {
+    return row.map((col, x) => {
+      return update({ x, y, seatMap })
+    })
+  })
+}
+
+const update = ({ x, y, seatMap }) => {
+  let next = seatMap[y][x]
+  switch (seatMap[y][x]) {
+    case '.':
+      // Floor (.) never changes; seats don't move, and nobody sits on the floor.
+      next = seatMap[y][x]
+      break
+    case 'L':
+      // If a seat is empty (L) and there are no occupied seats adjacent to it, the seat becomes occupied.
+      if (occupiedNearby({ x, y, seatMap }) === 0) {
+        next = '#'
+      }
+      break
+    case '#':
+      // If a seat is occupied (#) and four or more seats adjacent to it are also occupied, the seat becomes empty.
+      // We subtract 1 so we don't count the target seat
+      if (occupiedNearby({ x, y, seatMap }) - 1 >= 4) {
+        next = 'L'
+      }
+      break
+    default:
+      // Otherwise, the seat's state does not change.
+      next = seatMap[y][x]
+  }
+
+  return next
+}
+
+module.exports = {
+  format,
+  parse,
+  advance
+}

2020/day-11/seating.test.js

@@ -0,0 +1,99 @@
+/* eslint-env mocha */
+const { expect } = require('chai')
+const { format, parse, advance } = require('./seating')
+
+const testData = [
+`L.LL.LL.LL
+LLLLLLL.LL
+L.L.L..L..
+LLLL.LL.LL
+L.LL.LL.LL
+L.LLLLL.LL
+..L.L.....
+LLLLLLLLLL
+L.LLLLLL.L
+L.LLLLL.LL`
+]
+testData.push(
+`#.##.##.##
+#######.##
+#.#.#..#..
+####.##.##
+#.##.##.##
+#.#####.##
+..#.#.....
+##########
+#.######.#
+#.#####.##`
+)
+testData.push(
+`#.LL.L#.##
+#LLLLLL.L#
+L.L.L..L..
+#LLL.LL.L#
+#.LL.LL.LL
+#.LLLL#.##
+..L.L.....
+#LLLLLLLL#
+#.LLLLLL.L
+#.#LLLL.##`
+)
+testData.push(
+`#.##.L#.##
+#L###LL.L#
+L.#.#..#..
+#L##.##.L#
+#.##.LL.LL
+#.###L#.##
+..#.#.....
+#L######L#
+#.LL###L.L
+#.#L###.##`
+)
+testData.push(
+`#.#L.L#.##
+#LLL#LL.L#
+L.L.L..#..
+#LLL.##.L#
+#.LL.LL.LL
+#.LL#L#.##
+..L.L.....
+#L#LLLL#L#
+#.LLLLLL.L
+#.#L#L#.##`
+)
+testData.push(
+`#.#L.L#.##
+#LLL#LL.L#
+L.#.L..#..
+#L##.##.L#
+#.#L.LL.LL
+#.#L#L#.##
+..L.L.....
+#L#L##L#L#
+#.LLLLLL.L
+#.#L#L#.##`
+)
+
+describe('--- Day 11: Seating System ---', () => {
+  describe('Part 1', () => {
+    describe('advance()', () => {
+      it('advances the seating state', () => {
+        const results = testData.map((data) => {
+          return format(
+            advance(
+              parse(data)
+            )
+          )
+        })
+
+        for (let x = 1; x < testData.length; x++) {
+          console.debug('Step', x)
+          expect(results[x - 1]).to.equal(testData[x])
+        }
+        const finalOccupancy = (results[results.length - 1].match(/#/g) || []).length
+        expect(finalOccupancy).to.equal(37)
+      })
+    })
+  })
+})