day15, part2

day14/dayFourteen.go

@@ -0,0 +1,216 @@
+package day14
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strings"
+)
+
+func Run() int {
+	fmt.Println("hello day 14")
+
+	field := ReadPlatform("day14/input")
+	fmt.Println(field.String())
+
+	// fmt.Printf("> lines for field %+v\n", field.UpIndices())
+	// field.Move(field.Height(), field.UpIndices())
+	cycles := 1000000000
+	states := make(map[string]int)
+	// 2023/12/14 11:50:32 >>> found loop. known state after 10 equal to one after 3
+
+	var loopLen, initialStretch int
+
+	for i := 1; i <= cycles; i++ {
+		field.DoSpinCycle()
+		// fmt.Println(field.String())
+
+		stringRepr := field.String()
+		prevIter, known := states[stringRepr]
+		if known {
+			log.Printf(">>> found loop. known state after %d equal to one after %d", i, prevIter)
+			initialStretch = prevIter
+			loopLen = i - prevIter
+			break
+		}
+
+		states[stringRepr] = i
+
+		if i % 100000 == 0 {
+			log.Print("done ", i, " cycles")
+		}
+	}
+
+	// field is already in a 'loop' state.
+	// so we've already done 'initial stretch' so to make field in same state as after 'cycles'
+	// i only need to check rest of (cycles - initialStretch)
+	movesToMake := (cycles - initialStretch)%loopLen
+	log.Printf(">>> data: initial steps %d, loop len %d. to do same as %d iterations i need %d", initialStretch, loopLen, cycles, movesToMake)
+
+	for i := 1; i <= movesToMake; i++ {
+		field.DoSpinCycle()
+		// fmt.Println(field.String())
+	}
+
+	// north rock load
+	return field.NorthLoad()
+}
+
+const Rock rune = 'O'
+const Wall rune = '#'
+const Space rune = '.'
+
+type Platform struct {
+	Rocks [][]rune
+}
+
+func (p *Platform) Height() int {
+	return len(p.Rocks)
+}
+func (p *Platform) Width() int {
+	return len(p.Rocks[0])
+}
+
+func ReadPlatform(filename string) Platform {
+	bytes, err := os.ReadFile(filename)
+	if err != nil {
+		panic(fmt.Sprint("cannot read file: ", filename))
+	}
+	text := string(bytes)
+	text = strings.TrimSpace(text)
+	lines := strings.Split(text, "\n")
+
+	rocks := make([][]rune, len(lines))
+	for i, line := range lines {
+		rocks[i] = []rune(line)
+	}
+
+	return Platform{
+		Rocks: rocks,
+	}
+}
+
+func (p *Platform) String() string {
+	text := "\n"
+	for _, row := range p.Rocks {
+		text += string(row)
+		text += "\n"
+	}
+
+	return text
+}
+
+type Coord struct{ Row, Col int }
+
+// indices for moving UP, from down to up
+func (p *Platform) UpIndices() [][]Coord {
+	lines := make([][]Coord, 0)
+	for col := 0; col < p.Width(); col++ {
+		line := make([]Coord, 0)
+		for row := 0; row < p.Height(); row++ {
+			line = append(line, Coord{Row: row, Col: col})
+		}
+		lines = append(lines, line)
+	}
+	return lines
+}
+
+// indices for moving DOWN, from up to down
+func (p *Platform) DownIndices() [][]Coord {
+	lines := make([][]Coord, 0)
+	for col := 0; col < p.Width(); col++ {
+		line := make([]Coord, 0)
+		for row := p.Height() - 1; row >= 0; row-- {
+			line = append(line, Coord{Row: row, Col: col})
+		}
+		lines = append(lines, line)
+	}
+	return lines
+}
+
+// indices for moving RIGHT from right to left
+func (p *Platform) RightIndices() [][]Coord {
+	lines := make([][]Coord, 0)
+	for row := 0; row < p.Height(); row++ {
+		line := make([]Coord, 0)
+		for col := p.Width() - 1; col >= 0; col-- {
+			line = append(line, Coord{Row: row, Col: col})
+		}
+		lines = append(lines, line)
+	}
+	return lines
+}
+
+// indices for moving LEFT, from left to right
+func (p *Platform) LeftIndices() [][]Coord {
+	lines := make([][]Coord, 0)
+	for row := 0; row < p.Height(); row++ {
+		line := make([]Coord, 0)
+		for col := 0; col < p.Width(); col++ {
+			line = append(line, Coord{Row: row, Col: col})
+		}
+		lines = append(lines, line)
+	}
+	return lines
+}
+
+func (p *Platform) SymbAt(coord Coord) rune {
+	return p.Rocks[coord.Row][coord.Col]
+}
+func (p *Platform) SetSymbAt(coord Coord, symb rune) {
+	p.Rocks[coord.Row][coord.Col] = symb
+}
+
+func (p *Platform) Move(n int, lines [][]Coord) {
+	for _, line := range lines {
+		moveSize := 0
+		for i, coord := range line {
+			symb := p.SymbAt(coord)
+			switch symb {
+			case Space:
+				moveSize += 1
+				if moveSize > n {
+					moveSize = n
+				}
+			case Wall:
+				moveSize = 0
+			case Rock:
+				if moveSize == 0 {
+					continue
+				}
+				// get coord for moveSize back. and set that to 'o'
+				// and set current to '.'
+				// panic if that place is not '.' i guess
+				moveTo := line[i-moveSize]
+				symbAtTarget := p.SymbAt(moveTo)
+				if symbAtTarget != Space {
+					panic(fmt.Sprintf("attempting to move %+v to %+v, target symbol is %s, not '.'",
+						coord, moveTo, string(symbAtTarget)))
+				}
+				p.SetSymbAt(moveTo, Rock)
+				p.SetSymbAt(coord, Space)
+			}
+		}
+	}
+}
+
+func (p *Platform) NorthLoad() int {
+	total := 0
+	height := p.Height()
+	for i, row := range p.Rocks {
+		for _, symb := range row {
+			if symb == Rock {
+				total += (height - i)
+			}
+		}
+	}
+	return total
+}
+
+func (p *Platform) DoSpinCycle() {
+	// north, west, south, east - till the end
+	p.Move(p.Height(), p.UpIndices())
+	p.Move(p.Width(), p.LeftIndices())
+	p.Move(p.Height(), p.DownIndices())
+	p.Move(p.Width(), p.RightIndices())
+}

day14/example

@@ -0,0 +1,10 @@
+O....#....
+O.OO#....#
+.....##...
+OO.#O....O
+.O.....O#.
+O.#..O.#.#
+..O..#O..O
+.......O..
+#....###..
+#OO..#....

day14/input

@@ -0,0 +1,100 @@
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day15/dayFifteen.go

@@ -0,0 +1,148 @@
+package day15
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"regexp"
+	"slices"
+	"strconv"
+	"strings"
+)
+
+func Run() int {
+	fmt.Println("hello day 15")
+	log.Println("hello day 15")
+	filename := "day15/input"
+	bytes, err := os.ReadFile(filename)
+	if err != nil {
+		panic(fmt.Sprint("error reading file ", filename))
+	}
+	text := string(bytes)
+	text = strings.TrimSpace(text)
+	instructions := strings.Split(text, ",")
+
+	result := 0
+
+	boxes := make([]Box, 256)
+	for i, box := range boxes {
+		box.Focals = make(map[string]int)
+		boxes[i] = box
+	}
+
+	for _, instructionStr := range instructions {
+		i := ReadInstruction(instructionStr)
+		box := boxes[i.Box]
+		box.Act(i)
+		boxes[i.Box] = box
+
+		// result += ASCIIStringHash(instruction)
+	}
+
+	for i, box := range boxes {
+		if len(box.Labels) != 0 {
+			log.Printf("%d box %+v final state\n", i, box)
+		}
+		result += (i + 1) * box.FocusingPower()
+	}
+
+	return result
+}
+
+type Box struct {
+	Labels []string
+	Focals map[string]int
+}
+
+func (b *Box)Act(i Instruction) {
+	log.Printf("for box %+v instruction \n%s\n", b, i.String())
+	switch i.Action {
+    case Put:
+		_, found := b.Focals[i.Label]
+		if !found {
+			b.Labels = append(b.Labels, i.Label)
+		}
+		b.Focals[i.Label] = i.LensFocal
+
+	case Remove:
+		_, found := b.Focals[i.Label]
+		if !found {
+			return
+		}
+		index := slices.Index(b.Labels, i.Label)
+		delete(b.Focals, i.Label)
+		b.Labels = slices.Delete(b.Labels, index, index+1)
+	}
+	log.Printf("result : %+v\n", b)
+	return
+}
+
+func (b *Box)FocusingPower() int {
+	result := 0
+	for i, label := range b.Labels {
+		result += (i + 1) * b.Focals[label]
+	}
+	return result
+}
+
+type Action rune
+
+const (
+	Put    Action = '='
+	Remove        = '-'
+)
+
+type Instruction struct {
+	Label     string
+	Box       int
+	Action    Action
+	LensFocal int
+}
+
+func (i *Instruction) String() string {
+	operation := ""
+	switch i.Action {
+	case Put:
+		operation = "put into"
+	case Remove:
+		operation = "remove from"
+	}
+	return fmt.Sprintf("%s\t\t%d of focal %d %s", operation, i.Box, i.LensFocal, i.Label)
+}
+
+func ReadInstruction(str string) Instruction {
+	result := Instruction{}
+
+	re := regexp.MustCompile(`(?P<label>\D+)(?P<operation>[=\-])(?P<focal>\d*)`)
+	// log.Println("in str ", str)
+	fields := re.FindStringSubmatch(str)
+	// log.Printf("in %s found %+v", str, fields)
+
+	operation := fields[2]
+	operationRune := []rune(operation)[0]
+	result.Action = Action(operationRune)
+
+	if operationRune == '=' {
+		focalStr := fields[3]
+		focal, err := strconv.Atoi(focalStr)
+		if err != nil {
+			panic(fmt.Sprint("error reading focal from ", str))
+		}
+		result.LensFocal = focal
+	}
+
+	result.Label = fields[1]
+	result.Box = ASCIIStringHash(result.Label)
+
+	return result
+}
+
+func ASCIIStringHash(str string) int {
+	result := 0
+	for _, symb := range str {
+		result += int(symb)
+		result *= 17
+		result %= 256
+	}
+	return result
+}

day15/example

@@ -0,0 +1 @@
+rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7

main.go

@@ -3,12 +3,12 @@ package main
 import (
 	"log"
 
-	"sunshine.industries/aoc2023/day13"
+	"sunshine.industries/aoc2023/day15"
 )
 
 func main() {
 	log.Print("> starting run:")
 
-	result := day13.Run()
+	result := day15.Run()
-	log.Printf("day13 result: %d\n****\n", result)
+	log.Printf("day15 result: %d\n****\n", result)
 }