Merge pull request #5 from amclin/feature/2018-day-12

Feature/2018 day 12 part 2

Author: developher-net

2018/day-12/20-generations.txt

@@ -0,0 +1,22 @@
+Generating 20 generations from the input looks like this:
+..#...#...##..####..##.####.#...#...#.#.#.#......##....#....######.####.##..#..#..##.##..##....#######.....................
+..##..##.#.#....##...##..#..##..##...#######....#.##...##..#..###.#..#.#.#.######..##.#...##..#..######....................
+.#.#...#.####..#.##.#.#.###..#...##.#..######....#.##.#.#.###..#..###.#####..####...#.##.#.#.###...#####...................
+..###...#..##.#.#.#.####.##.###.#.#.##...#####....#.#.####.##.###..#.#..###....###...#.#.####.###.#..####..................
+.#.###..##..#.######..#.#.##.#..####.##.#..####....###..#.#.##.##.#.###..###..#.###...###..#.#.#..##...###.................
+..#.##...#.#.#..####.#.###.#.##...#.#.#.##...###..#.##.#.###.##.#.##.##...##.#.#.###.#.##.#.#####..##.#.###................
+...#.##...#####...#..##.#..##.##...#####.##.#.##.#.#.#.##.#.#.#.##.##.##.#.#.####.#..##.#.##..###...#.##.###...............
+....#.##.#..####..##..#.##..##.##.#..##.#.#.##.#.######.#.######.##.##.#.####..#..##..#.##.#...###...#.##.###..............
+.....#.#.##...##...#.#.#.#...##.#.##..#.####.#.##..###..##..###.#.##.#.##..##.###..#.#.#.#.##.#.###...#.##.###.............
+......###.##.#.##...#######.#.#.##.#.#.#..#..##.#...##...#...#..##.#.##.#...##.##.#.#######.#.##.###...#.##.###............
+.....#.#.#.#.##.##.#..####..####.#.#########..#.##.#.##..##..##..#.##.#.##.#.##.#.##..####..##.##.###...#.##.###...........
+......#######.##.#.##...##....#..##..#######.#.#.#.##.#...#...#.#.#.#.##.#.##.#.##.#....##...##.##.###...#.##.###..........
+.....#..####.#.#.##.##.#.##...##..#....####..######.#.##..##...#######.#.##.#.##.#.##..#.##.#.##.##.###...#.##.###.........
+.....##...#..####.##.#.##.##.#.#.###..#..##....###..##.#...##.#..####..##.#.##.#.##.#.#.#.#.##.##.##.###...#.##.###........
+....#.##..##...#.#.#.##.##.#.####.##.###..##..#.##...#.##.#.#.##...##...#.##.#.##.#.########.##.##.##.###...#.##.###.......
+.....#.#...##...#####.##.#.##..#.#.##.##...#.#.#.##...#.#.####.##.#.##...#.#.##.#.##..#####.#.##.##.##.###...#.##.###......
+......###.#.##.#..##.#.#.##.#.#.###.##.##...#####.##...###..#.#.#.##.##...###.#.##.#....##..##.##.##.##.###...#.##.###.....
+.....#.#..##.#.##..#.####.#.####.#.#.##.##.#..##.#.##.#.##.#.#####.##.##.#.#..##.#.##..#.#...##.##.##.##.###...#.##.###....
+......###..#.##.#.#.#..#..##..#..####.##.#.##..#.##.#.##.#.##..##.#.##.#.####..#.##.#.#.###.#.##.##.##.##.###...#.##.###...
+.....#.##.#.#.#.#########..#.###...#.#.#.##.#.#.#.#.##.#.##.#...#.##.#.##..##.#.#.#.####.#..##.##.##.##.##.###...#.##.###..
+......#.#.######..#######.#.#.###...#####.#.########.#.##.#.##...#.#.##.#...#.######..#..##..##.##.##.##.##.###...#.##.###.

2018/day-12/output/500-generations.png

@@ -0,0 +1,22 @@
+Generating 20 generations from the input looks like this:
+..#...#...##..####..##.####.#...#...#.#.#.#......##....#....######.####.##..#..#..##.##..##....#######.....................
+..##..##.#.#....##...##..#..##..##...#######....#.##...##..#..###.#..#.#.#.######..##.#...##..#..######....................
+.#.#...#.####..#.##.#.#.###..#...##.#..######....#.##.#.#.###..#..###.#####..####...#.##.#.#.###...#####...................
+..###...#..##.#.#.#.####.##.###.#.#.##...#####....#.#.####.##.###..#.#..###....###...#.#.####.###.#..####..................
+.#.###..##..#.######..#.#.##.#..####.##.#..####....###..#.#.##.##.#.###..###..#.###...###..#.#.#..##...###.................
+..#.##...#.#.#..####.#.###.#.##...#.#.#.##...###..#.##.#.###.##.#.##.##...##.#.#.###.#.##.#.#####..##.#.###................
+...#.##...#####...#..##.#..##.##...#####.##.#.##.#.#.#.##.#.#.#.##.##.##.#.#.####.#..##.#.##..###...#.##.###...............
+....#.##.#..####..##..#.##..##.##.#..##.#.#.##.#.######.#.######.##.##.#.####..#..##..#.##.#...###...#.##.###..............
+.....#.#.##...##...#.#.#.#...##.#.##..#.####.#.##..###..##..###.#.##.#.##..##.###..#.#.#.#.##.#.###...#.##.###.............
+......###.##.#.##...#######.#.#.##.#.#.#..#..##.#...##...#...#..##.#.##.#...##.##.#.#######.#.##.###...#.##.###............
+.....#.#.#.#.##.##.#..####..####.#.#########..#.##.#.##..##..##..#.##.#.##.#.##.#.##..####..##.##.###...#.##.###...........
+......#######.##.#.##...##....#..##..#######.#.#.#.##.#...#...#.#.#.#.##.#.##.#.##.#....##...##.##.###...#.##.###..........
+.....#..####.#.#.##.##.#.##...##..#....####..######.#.##..##...#######.#.##.#.##.#.##..#.##.#.##.##.###...#.##.###.........
+.....##...#..####.##.#.##.##.#.#.###..#..##....###..##.#...##.#..####..##.#.##.#.##.#.#.#.#.##.##.##.###...#.##.###........
+....#.##..##...#.#.#.##.##.#.####.##.###..##..#.##...#.##.#.#.##...##...#.##.#.##.#.########.##.##.##.###...#.##.###.......
+.....#.#...##...#####.##.#.##..#.#.##.##...#.#.#.##...#.#.####.##.#.##...#.#.##.#.##..#####.#.##.##.##.###...#.##.###......
+......###.#.##.#..##.#.#.##.#.#.###.##.##...#####.##...###..#.#.#.##.##...###.#.##.#....##..##.##.##.##.###...#.##.###.....
+.....#.#..##.#.##..#.####.#.####.#.#.##.##.#..##.#.##.#.##.#.#####.##.##.#.#..##.#.##..#.#...##.##.##.##.###...#.##.###....
+......###..#.##.#.#.#..#..##..#..####.##.#.##..#.##.#.##.#.##..##.#.##.#.####..#.##.#.#.###.#.##.##.##.##.###...#.##.###...
+.....#.##.#.#.#.#########..#.###...#.#.#.##.#.#.#.#.##.#.##.#...#.##.#.##..##.#.#.#.####.#..##.##.##.##.##.###...#.##.###..
+......#.#.######..#######.#.#.###...#####.#.########.#.##.#.##...#.#.##.#...#.######..#..##..##.##.##.##.##.###...#.##.###.

2018/day-12/output/500-generations.txt

@@ -10,15 +10,55 @@ const initialState = '#...#...##..####..##.####.#...#...#.#.#.#......##....#....
 
 const init = (data) => {
   const rules = data
-  const plantTracker = new Plants(initialState, rules)
+  let plantTracker = new Plants(initialState, rules)
   const generations = 20
   for (let gen = 1; gen <= generations; gen++) {
     plantTracker.advance()
   }
   console.log(`Generating ${generations} generations from the input looks like this:`)
   plantTracker.display()
   const answer = plantTracker.getCheckSum(generations)
-  const answer2 = ''
+
+  // Start for part 2
+  const generations2 = 500
+  for (let gen = generations + 1; gen <= generations2; gen++) {
+    plantTracker.advance()
+  }
+  console.log(`Generating ${generations2} generations from the input looks like this:`)
+  plantTracker.display()
+
+  // 500 generations takes about 30s, so running 50B generations isn't possible. It's
+  // clear looking at the log there's a "Game of Life"-style glider.
+  // See output/500-generations.txt and output/500-generations.png
+  // This probably is reflected in a pattern in the checksum.
+  let prevCheckSum = 0
+  let prevDelta = 0
+  const stableThreshold = 5 // The number of sequentially identical deltas necessary to determine stabilization
+  const stableDeltas = Array(stableThreshold).fill(0)
+  let stableGeneration = 0
+  let stableCheckSum = 0
+  for (let gen = 0; gen <= generations2; gen++) {
+    const checkSum = plantTracker.getCheckSum(gen)
+    const delta = checkSum - prevCheckSum
+    console.log(`Generation ${gen} checksum: ${plantTracker.getCheckSum(gen)} which is Δ of ${delta})`)
+
+    // When delta matches previous generation, we may have reached stabilization
+    if (delta === prevDelta) {
+      stableDeltas.shift()
+      stableDeltas.push(delta)
+      // Reached true stable point when there are N deltas in a row that are the same.
+      if (stableDeltas.filter((Δ) => Δ === delta).length === stableDeltas.length) {
+        stableCheckSum = checkSum
+        stableGeneration = gen
+        break
+      }
+    }
+    prevCheckSum = checkSum
+    prevDelta = delta
+  }
+  console.log(`At generation ${stableGeneration} the Δ is ${stableDeltas[0]} and the checksum is ${stableCheckSum}.`)
+  // Calculate the checksum for 50B generations (minus the generation we're already at)
+  const answer2 = (stableDeltas[0] * (50000000000 - stableGeneration - 1)) + stableCheckSum
 
   console.log(`-- Part 1 --`)
   console.log(`Answer: ${answer}`)