complete day 7

06-a.kts

@@ -0,0 +1,78 @@
+import java.util.Scanner
+
+enum class Direction {
+    NORTH {
+        override fun moveFrom(row: Int, col: Int): Pair<Int, Int> {
+            return Pair(row-1, col)
+        }
+    }, SOUTH {
+        override fun moveFrom(row: Int, col: Int): Pair<Int, Int> {
+            return Pair(row+1, col)
+        }
+    }, WEST {
+        override fun moveFrom(row: Int, col: Int): Pair<Int, Int> {
+            return Pair(row, col-1)
+        }
+    }, EAST {
+        override fun moveFrom(row: Int, col: Int): Pair<Int, Int> {
+            return Pair(row, col+1)
+        }
+    };
+
+    fun turnRight(): Direction {
+        return when (this) {
+            NORTH -> EAST
+            EAST -> SOUTH
+            SOUTH -> WEST
+            WEST -> NORTH
+        }
+    }
+
+    abstract fun moveFrom(row: Int, col: Int): Pair<Int, Int>
+}
+
+val scanner = Scanner(System.`in`)
+
+val map = ArrayList<Array<Char>>()
+
+var rows = 0
+var guardRow = -1
+var guardCol = -1
+while (scanner.hasNextLine()) {
+    val line = scanner.nextLine()
+    val pos = line.indexOf('^')
+    if (pos != -1) {
+        guardRow = rows
+        guardCol = pos
+    }
+    val chars = line.toCharArray().toTypedArray()
+    map.add(chars)
+    rows++
+}
+
+var facing = Direction.NORTH
+
+var visitedCount = 0
+walk@ while (true) {
+    if (map[guardRow][guardCol] != 'X') {
+        visitedCount++
+    }
+    map[guardRow][guardCol] = 'X'
+
+    var seeking = true
+    do {
+        val (nextRow, nextCol) = facing.moveFrom(guardRow, guardCol)
+        if (nextRow < 0 || nextRow >= map.size || nextCol < 0 || nextCol >= map[nextCol].size) {
+            break@walk
+        }
+
+        if (map[nextRow][nextCol] == '#') {
+            facing = facing.turnRight()
+        } else {
+            guardRow = nextRow
+            guardCol = nextCol
+            seeking = false
+        }
+    } while (seeking)
+}
+println(visitedCount)

07-a.kts

@@ -0,0 +1,30 @@
+import java.math.BigInteger
+import java.util.*
+
+val scanner = Scanner(System.`in`)
+
+var sum: BigInteger = BigInteger.ZERO
+while (scanner.hasNextLine()) {
+    val line = scanner.nextLine()
+    val numbersInLine = line.split("[: ]+".toRegex()).map(String::toBigInteger)
+    val target = numbersInLine.first()
+    val numbers = numbersInLine.drop(1)
+    val possibleResults = findAllPossibleResult(setOf(numbers.first()), numbers.drop(1))
+    if (possibleResults.contains(target)) {
+        sum += target
+    }
+}
+println(sum)
+
+fun findAllPossibleResult(partialResults: Set<BigInteger>, numbers: List<BigInteger>): Set<BigInteger> {
+    if (numbers.isEmpty()) return partialResults
+
+    val head = numbers.first()
+    val tail = numbers.drop(1)
+    val newResults = partialResults.fold(HashSet<BigInteger>()) { r, p ->
+        r.add(p.plus(head))
+        r.add(p.times(head))
+        r
+    }
+    return findAllPossibleResult(newResults, tail)
+}

07-b.kts

@@ -0,0 +1,32 @@
+import java.math.BigInteger
+import java.util.*
+
+val scanner = Scanner(System.`in`)
+
+var sum: BigInteger = BigInteger.ZERO
+while (scanner.hasNextLine()) {
+    val line = scanner.nextLine()
+    val numbersInLine = line.split("[: ]+".toRegex()).map(String::toBigInteger)
+    val target = numbersInLine.first()
+    val numbers = numbersInLine.drop(1)
+    val possibleResults = findAllPossibleResult(setOf(numbers.first()), numbers.drop(1))
+    if (possibleResults.contains(target)) {
+        sum += target
+//        println(line)
+    }
+}
+println(sum)
+
+fun findAllPossibleResult(partialResults: Set<BigInteger>, numbers: List<BigInteger>): Set<BigInteger> {
+    if (numbers.isEmpty()) return partialResults
+
+    val head = numbers.first()
+    val tail = numbers.drop(1)
+    val newResults = partialResults.fold(HashSet<BigInteger>()) { r, p ->
+        r.add("$p$head".toBigInteger())
+        r.add(p.plus(head))
+        r.add(p.times(head))
+        r
+    }
+    return findAllPossibleResult(newResults, tail)
+}