Day 18

days/18/1.ps1

+Set-StrictMode -Version latest
+$lines = Get-Content -Path $PSScriptRoot\input | Select -First 1024
+$xSize=70
+$ySize=70
+
+$grid=@()
+for($y=0;$y -le $ySize;$y++) {
+    $line=@()
+    for($x=0;$x -le $xSize;$x++) {
+        $line+="."
+    }
+    $grid+=,$line
+}
+function drawGrid {
+    $grid | ForEach-Object {
+        $_ -join ' ' | Write-Host 
+    }
+}
+
+$lines | ForEach-Object {
+    $parts = $_ -split ','
+    [int]$x=$parts[0]
+    [int]$y=$parts[1]
+    $grid[$y][$x]="#"
+}
+
+$grid[0][0]=0
+function getValue {
+    param($x,$y, $xOffset, $yOffset)
+    $x+=$xOffset
+    $y+=$yOffset
+    if($y -gt $ySize -or $x -gt $xSize) {
+        return 100000
+    }
+    $value = $grid[$y][$x]
+    if($value -eq "#" -or $value -eq ".") {
+        $value = 100000
+    }
+    return $value
+}
+
+function doCell {
+    param($x, $y)
+    $current=$grid[$y][$x]
+    if($current -eq "#") {
+        return $false
+    }
+    if($current -eq ".") {
+        $current = 100000
+    }
+    $numbers = @($current)
+    $numbers+=getValue $x $y 0 -1
+    $numbers+=getValue $x $y 0 1
+    $numbers+=getValue $x $y -1 0
+    $numbers+=getValue $x $y 1 0
+
+    $measurement = $numbers | measure-object -Minimum
+    $min = $measurement.Minimum
+    $min += 1
+    if($current -gt $min) {
+        $grid[$y][$x]=$min
+        $cellsChanged+=1
+        return $true
+    } else {
+        return $false
+    }
+}
+$changed=1
+while($changed -ge 1) {
+    $changed=0
+    for($y=0;$y -le $ySize;$y++) {
+        for($x=0;$x -le $xSize;$x++) {
+            $singleChanged = doCell $x $y
+            if($singleChanged) {
+                $changed+=1
+            }
+        }
+        for($x=$xSize;$x -ge 0;$x--) {
+            $singleChanged = doCell $x $y
+            if($singleChanged) {
+                $changed+=1
+            }
+        }
+    }
+    for($y=$ySize;$y -ge 0;$y--) {
+        for($x=0;$x -le $xSize;$x++) {
+            $singleChanged = doCell $x $y
+            if($singleChanged) {
+                $changed+=1
+            }
+        }
+        for($x=$xSize;$x -ge 0;$x--) {
+            $singleChanged = doCell $x $y
+            if($singleChanged) {
+                $changed+=1
+            }
+        }
+    }
+    Write-Host "$changed cells changed"
+}
+
+$solution = $grid[$ySize][$xSize]
+Write-Host "solution: $solution"
\ No newline at end of file

days/18/2.ps1

+Set-StrictMode -Version latest
+$xSize=70
+$ySize=70
+
+$lines = Get-Content -Path $PSScriptRoot\input
+function getValue {
+    param($x,$y, $xOffset, $yOffset)
+    $x+=$xOffset
+    $y+=$yOffset
+    if($y -gt $ySize -or $x -gt $xSize) {
+        return $false
+    }
+    return $grid[$y][$x] -eq "X"
+}
+
+function doCell {
+    param($x, $y)
+    $current=$grid[$y][$x]
+    if($current -ne ".") {
+        return $false
+    }
+    $above=getValue $x $y 0 -1
+    $below=getValue $x $y 0 1
+    $left=getValue $x $y -1 0
+    $right=getValue $x $y 1 0
+    if($above -or $below -or $left -or $right) {
+        $grid[$y][$x]="X"
+        return $true
+    } else {
+        return $false
+    }
+}
+function withAmount {
+    param($amount)
+    $grid=@()
+    for($y=0;$y -le $ySize;$y++) {
+        $line=@()
+        for($x=0;$x -le $xSize;$x++) {
+            $line+="."
+        }
+        $grid+=,$line
+    }    
+    $lines | Select -First $amount | ForEach-Object {
+        $parts = $_ -split ','
+        [int]$x=$parts[0]
+        [int]$y=$parts[1]
+        $grid[$y][$x]="#"
+    }
+    $grid[0][0]="X"
+    $changed=1
+    while($changed -ge 1) {
+        $changed=0
+        for($y=0;$y -le $ySize;$y++) {
+            for($x=0;$x -le $xSize;$x++) {
+                $singleChanged = doCell $x $y
+                if($singleChanged) {
+                    $changed+=1
+                }
+            }
+            for($x=$xSize;$x -ge 0;$x--) {
+                $singleChanged = doCell $x $y
+                if($singleChanged) {
+                    $changed+=1
+                }
+            }
+        }
+        for($y=$ySize;$y -ge 0;$y--) {
+            for($x=0;$x -le $xSize;$x++) {
+                $singleChanged = doCell $x $y
+                if($singleChanged) {
+                    $changed+=1
+                }
+            }
+            for($x=$xSize;$x -ge 0;$x--) {
+                $singleChanged = doCell $x $y
+                if($singleChanged) {
+                    $changed+=1
+                }
+            }
+        }
+        Write-Host "$changed cells changed"
+        if($grid[$ySize][$xSize] -eq "X") {
+            return $true
+        }
+    }
+    return $false
+}
+
+$min=0
+$max=$lines.Length
+while($min -ne $max) {
+    Write-Host "$min-$max"
+    $distance=$max-$min
+    [int]$avg=$distance/2+$min
+    Write-Host "avg: $avg"
+    $finished=withAmount $avg
+    Write-Host "finished: $finished"
+    if($distance -eq 1) {
+        if($finished) {
+            $min=$avg
+            $max=$avg
+        } else {
+            $min=$avg-1
+            $max=$avg-1
+        }
+    } elseif($finished) {
+        $min=$avg
+    } else {
+        $max=$avg
+    }
+}
+Write-Host "solution:$($lines[$min])"