Refactoring Day 14 to use entropy to find the least random configuration of points to detect the tree

jwcarman · jwcarman · commit 8196ed3b65ca · 2024-12-18T23:11:33.000-05:00
diff --git a/src/main/kotlin/adventofcode/day14/RestroomRedoubt.kt b/src/main/kotlin/adventofcode/day14/RestroomRedoubt.kt
@@ -91,6 +91,8 @@ fun List<Point2D>.calculateShannonEntropy(maxX: Int, maxY: Int, gridWidth: Int,
         .sumOf { -it * ln(it) }
 }
 
+private const val GRID_WIDTH = 10
+private const val GRID_HEIGHT = 10
 
 fun String.findTree(): Int {
     val robots = parseRobots()
@@ -99,7 +101,7 @@ fun String.findTree(): Int {
     val sequences = robots.map { it.points(maxX, maxY) }
 
     val minEntropyT = (1..lcmInt(maxX, maxY)).minBy { t ->
-        sequences.map { it.next() }.calculateShannonEntropy(maxX, maxY, 10, 10)
+        sequences.map { it.next() }.calculateShannonEntropy(maxX, maxY, GRID_WIDTH, GRID_HEIGHT)
     }
     robots.map { it.move(minEntropyT, maxX, maxY) }.toSet().printGrid(maxX, maxY)
     return minEntropyT

Original file line number	Diff line number	Diff line change
`@@ -91,6 +91,8 @@ fun List<Point2D>.calculateShannonEntropy(maxX: Int, maxY: Int, gridWidth: Int,`
`91`	`91`	`.sumOf { -it * ln(it) }`
`92`	`92`	`}`
`93`	`93`
	`94`	`+private const val GRID_WIDTH = 10`
	`95`	`+private const val GRID_HEIGHT = 10`
`94`	`96`
`95`	`97`	`fun String.findTree(): Int {`
`96`	`98`	`val robots = parseRobots()`
`@@ -99,7 +101,7 @@ fun String.findTree(): Int {`
`99`	`101`	`val sequences = robots.map { it.points(maxX, maxY) }`
`100`	`102`
`101`	`103`	`val minEntropyT = (1..lcmInt(maxX, maxY)).minBy { t ->`
`102`		`- sequences.map { it.next() }.calculateShannonEntropy(maxX, maxY, 10, 10)`
	`104`	`+ sequences.map { it.next() }.calculateShannonEntropy(maxX, maxY, GRID_WIDTH, GRID_HEIGHT)`
`103`	`105`	`}`
`104`	`106`	`robots.map { it.move(minEntropyT, maxX, maxY) }.toSet().printGrid(maxX, maxY)`
`105`	`107`	`return minEntropyT`