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14-2023 Part 2 + 15-2023 both parts
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‎2023/Day14/README.md

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@@ -63,3 +63,56 @@ The total load is the sum of the load caused by all of the <em>rounded rocks</em
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Tilt the platform so that the rounded rocks all roll north. Afterward, <em>what is the total load on the north support beams?</em>
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## --- Part Two ---
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The parabolic reflector dish deforms, but not in a way that focuses the beam. To do that, you'll need to move the rocks to the edges of the platform. Fortunately, a button on the side of the control panel labeled "<em>spin cycle</em>" attempts to do just that!
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Each <em>cycle</em> tilts the platform four times so that the rounded rocks roll <em>north</em>, then <em>west</em>, then <em>south</em>, then <em>east</em>. After each tilt, the rounded rocks roll as far as they can before the platform tilts in the next direction. After one cycle, the platform will have finished rolling the rounded rocks in those four directions in that order.
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Here's what happens in the example above after each of the first few cycles:
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<pre>
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<code>After 1 cycle:
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.....#....
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....#...O#
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...OO##...
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.OO#......
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.....OOO#.
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.O#...O#.#
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....O#....
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......OOOO
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#...O###..
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#..OO#....
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After 2 cycles:
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.....#....
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....#...O#
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.....##...
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..O#......
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.....OOO#.
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.O#...O#.#
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....O#...O
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.......OOO
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#..OO###..
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#.OOO#...O
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After 3 cycles:
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.....#....
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....#...O#
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.....##...
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..O#......
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.....OOO#.
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.O#...O#.#
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....O#...O
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.......OOO
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#...O###.O
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#.OOO#...O
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</code>
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</pre>
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This process should work if you leave it running long enough, but you're still worried about the north support beams. To make sure they'll survive for a while, you need to calculate the <em>total load</em> on the north support beams after <code>1000000000</code> cycles.
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In the above example, after <code>1000000000</code> cycles, the total load on the north support beams is <code><em>64</em></code>.
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Run the spin cycle for <code>1000000000</code> cycles. Afterward, <em>what is the total load on the north support beams?</em>
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‎2023/Day14/Solution.cs

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@@ -1,12 +1,6 @@
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using System;
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using System.Collections.Generic;
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using System.Collections.Immutable;
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using System.Linq;
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using System.Text.RegularExpressions;
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using System.Text;
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using adventofcode.Utils;
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using AngleSharp.Common;
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using AngleSharp.Html.Dom;
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namespace AdventOfCode.Y2023.Day14;
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@@ -80,6 +74,90 @@ public object PartOne(string input)
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public object PartTwo(string input)
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{
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return 0;
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// For part 2, I used Go/Golang, check out the go.txt file
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var grid = new Grid(input, true);
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long result = 0;
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for (var i = 0; i < 200; i++)
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{
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while (RollRocks(grid)) ;
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grid.Rotate(Orientation.East);
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while (RollRocks(grid)) ;
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grid.Rotate(Orientation.East);
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while (RollRocks(grid)) ;
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grid.Rotate(Orientation.East);
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while (RollRocks(grid)) ;
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grid.Rotate(Orientation.East);
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}
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var cycleVals = new List<long>();
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for (var i = 0; i < 200; i++)
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{
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while (RollRocks(grid)) ;
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grid.Rotate(Orientation.East);
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while (RollRocks(grid)) ;
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grid.Rotate(Orientation.East);
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while (RollRocks(grid)) ;
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grid.Rotate(Orientation.East);
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while (RollRocks(grid)) ;
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grid.Rotate(Orientation.East);
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var v = CalcLoad(grid);
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if (cycleVals.Contains(v))
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{
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var j = cycleVals.LastIndexOf(v);
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var cycleLen = (i - j);
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var q = (1000000000 - 200 - i -1) % cycleLen;
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var n = (q + j) % cycleLen;
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result = cycleVals[n];
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break;
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}
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cycleVals.Add(v);
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}
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return result;
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}
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private static bool RollRocks(Grid grid)
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{
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var didShift = false;
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for (var y = grid.MinY; y + 1 < grid.MaxY; y++)
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{
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for (var x = grid.MinX; x < grid.MaxX; x++)
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{
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if (grid[x, y] == '.' && grid[x, y + 1] == 'O')
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{
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grid[x, y + 1] = '.';
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grid[x, y] = 'O';
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didShift = true;
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}
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}
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}
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return didShift;
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}
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private static long CalcLoad(Grid grid)
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{
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var result = 0L;
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grid.Rotate(Orientation.South);
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for (var y = grid.MinY; y < grid.MaxY; y++)
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{
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for (var x = grid.MinX; x < grid.MaxX; x++)
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{
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if (grid[x, y] == 'O')
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{
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result += y + 1;
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}
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}
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}
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grid.Rotate(Orientation.South);
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return result;
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}
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}
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}

‎2023/Day14/go.txt

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package main
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import (
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"bytes"
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"fmt"
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"log"
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"os"
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"time"
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)
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const ObjRock = byte('O')
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const ObjEmpty = byte('.')
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var directions = [][]int{
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{0, -1}, // N
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{-1, 0}, // W
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{0, 1}, // S
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{1, 0}, // E
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}
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func tilt(grid [][]byte, dir []int) {
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width := len(grid[0])
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height := len(grid)
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startCol := 0
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colStep := 1
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if dir[0] == 1 {
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startCol = width - 1
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colStep = -1
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}
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startRow := 0
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rowStep := 1
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if dir[1] == 1 {
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startRow = height - 1
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rowStep = -1
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}
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for row := startRow; row < height && row >= 0; row += rowStep {
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for col := startCol; col < width && col >= 0; col += colStep {
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if grid[row][col] != ObjRock {
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continue
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}
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// walk into direction until obstacle
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c := col
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r := row
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for c+dir[0] >= 0 && c+dir[0] < width && r+dir[1] >= 0 && r+dir[1] < height && grid[r+dir[1]][c+dir[0]] == ObjEmpty {
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c += dir[0]
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r += dir[1]
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}
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// place rock at new position
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if r != row || c != col {
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grid[r][c] = ObjRock
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grid[row][col] = ObjEmpty
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}
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}
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}
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}
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func weight(grid [][]byte) int {
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width := len(grid[0])
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height := len(grid)
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weight := 0
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for row := 0; row < height; row++ {
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for col := 0; col < width; col++ {
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if grid[row][col] != ObjRock {
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continue
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}
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weight += height - row
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}
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}
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return weight
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}
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func isEqual(a [][]byte, b [][]byte) bool {
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for row := 0; row < len(a); row++ {
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if !bytes.Equal(a[row], b[row]) {
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return false
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}
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}
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return true
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}
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func copyGrid(a [][]byte) [][]byte {
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rows := make([][]byte, len(a))
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for i := range a {
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rows[i] = make([]byte, len(a[i]))
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copy(rows[i], a[i])
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}
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return rows
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}
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// Floyd's Tortoise and Hare algorithm
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// https://en.wikipedia.org/wiki/Cycle_detection
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func floyd(f func([][]byte), x0 [][]byte) (int, [][]byte) {
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hare := copyGrid(x0)
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tortoise := copyGrid(x0)
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f(tortoise)
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f(hare)
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f(hare)
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for !isEqual(tortoise, hare) {
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f(tortoise)
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f(hare)
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f(hare)
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}
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// move hare forward until start of next cycle
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// tortoise remains in place
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cycleLength := 1
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f(hare)
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for !isEqual(tortoise, hare) {
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f(hare)
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cycleLength += 1
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}
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// return length of cycle and current state of grid
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return cycleLength, hare
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}
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func main() {
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timeStart := time.Now()
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b, err := os.ReadFile("input.txt")
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if err != nil {
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log.Fatal(err)
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}
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grid := bytes.Split(bytes.TrimSpace(b), []byte("\n"))
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// pt1
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grid1 := copyGrid(grid)
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tilt(grid1, directions[0])
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pt1 := weight(grid1)
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timeElapsed := time.Since(timeStart)
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timeStart2 := time.Now()
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// part 2
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cycle := func(g [][]byte) {
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tilt(g, directions[0])
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tilt(g, directions[1])
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tilt(g, directions[2])
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tilt(g, directions[3])
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}
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cycleLength, state := floyd(cycle, grid)
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cyclesRemaining := 1e9 % cycleLength
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for i := 0; i < cyclesRemaining; i++ {
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cycle(state)
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}
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pt2 := weight(state)
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fmt.Printf("--- Day 14: Parabolic Reflector Dish ---\n")
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fmt.Printf("Part 1: %d | %.2fms\n", pt1, float64(timeElapsed.Microseconds())/1000)
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fmt.Printf("Part 2: %d | %.2fms\n", pt2, float64(time.Since(timeStart2).Microseconds())/1000)
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fmt.Printf("Time: %.2fms\n", float64(time.Since(timeStart).Microseconds())/1000)
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}

‎2023/Day14/input.in

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@@ -97,4 +97,4 @@ O..O.#O..OOO..O...O...#.......#O.OO....O..#...O.....O.#.OO....#.O.OO...O#...OOO#
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O....#....#O.####.O...#....O....#O..#O...O.O....O.O#..O.........O#.......O....O..O...#.##..O.OO.OO..
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.O###O...#OO.OO........O.O#.O.O....O.O...##.O#..###..........#..O#.O..O.OO.O..#O#OO..O#.O.##.O.OOO##
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#.#O#..O.#...O#..#.......O#..#...#...#O..#.O.....O...O.......#O.#...#OO.O....OO..O...#.#....#O......
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..O.#O.O.O#..#.O...#.....#..O..##..O......O.OO.O.###.....#.O..O...OO#.OO.....#...OO#O..#..#O#...O..O
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..O.#O.O.O#..#.O...#.....#..O..##..O......O.OO.O.###.....#.O..O...OO#.OO.....#...OO#O..#..#O#...O..O

‎2023/Day14/input.refout

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