day 10, bigints to avoid overflow

Author: Matsemann

adventofcode2020/inputs/day10_example.txt

@@ -1,11 +1,31 @@
-16
-10
-15
-5
-1
+28
+33
+18
+42
+31
+14
+46
+20
+48
+47
+24
+23
+49
+45
+19
+38
+39
 11
+1
+32
+25
+35
+8
+17
 7
-19
-6
-12
-4
+9
+4
+2
+34
+10
+3

adventofcode2020/src/main/kotlin/com/matsemann/adventofcode2020/Day10.kt

@@ -30,14 +30,16 @@ fun day10_2(lines: List<String>,) {
         .plus(numbers.last() + 3)
         .sorted()
 
-    val counts = mutableMapOf<Int, Int>()
-    counts[0] = 1
+    val counts = mutableMapOf<Int, BigInteger>()
+    counts[0] = BigInteger.ONE
 
     adaptors.forEach {
-        val sum = (counts[it - 3] ?: 0) + (counts[it - 2] ?: 0) + (counts[it-1] ?: 0)
+        val sum = (counts[it - 3] ?: BigInteger.ZERO) + (counts[it - 2] ?: BigInteger.ZERO) + (counts[it-1] ?: BigInteger.ZERO)
         counts[it] = sum
     }
-    println()
+
+    val ways = counts.maxOf { it.value }
+    println("ways: $ways")
 
 
     /*

adventofcode2020/src/test/kotlin/com/matsemann/adventofcode2020/Runner.kt

@@ -126,7 +126,7 @@ class Runner {
     }
     @Test
     fun day10_2Runner() {
-        val lines = getFileLines("inputs/day10_example.txt").toList()
+        val lines = getFileLines("inputs/day10_1.txt").toList()
         day10_2(lines)
     }