Day 5: Added timings and compared to a naive "String.substring" implementation

src/main/kotlin/com/basdado/adventofcode/Day5.kt

@@ -6,9 +6,12 @@ import kotlin.system.measureTimeMillis
 fun main() {
 
     val day = Day5()
-    println("Puzzle 1 time: " + measureTimeMillis { day.puzzle1() } + " ms")
+    println("Puzzle 1 linked list time: " + measureTimeMillis { day.puzzle1() } + " ms")
-    println("Puzzle 2 time: " + measureTimeMillis { day.puzzle2() } + " ms")
+    println("Puzzle 2 linked list time: " + measureTimeMillis { day.puzzle2() } + " ms")
 
+    val dayNaive = Day5Substring()
+    println("Puzzle 1 substring time: " + measureTimeMillis { dayNaive.puzzle1() } + " ms")
+    println("Puzzle 2 substring time: " + measureTimeMillis { dayNaive.puzzle2() } + " ms")
 }
 
 class Day5 {
@@ -123,4 +126,38 @@ class Day5 {
             return "" + char
         }
     }
+}
+
+class Day5Substring {
+    fun puzzle1() {
+        println(react(lines("/day/5/input.txt").findFirst().get()).length)
+    }
+
+    fun puzzle2() {
+        val fullPolymerString = lines("/day/5/input.txt").findFirst().get()
+        println(fullPolymerString.chars()
+            .distinct().boxed()
+            .map { it.toChar() }.map { it.toString() }
+            .map { it.toUpperCase() }
+            .distinct()
+            .mapToInt { react(fullPolymerString.replace(it.toString(), "", true)).length }
+            .min()!!)
+    }
+
+    fun react(polymer: String): String {
+
+        var curPolymer = polymer
+
+        var i = 0
+        while(i < curPolymer.length - 1) {
+            if (reactsWith(curPolymer[i], curPolymer[i + 1])) {
+                curPolymer = curPolymer.substring(0, i) + curPolymer.substring(i + 2)
+                i = if (i == 0) -1 else i - 2
+            }
+            i++
+        }
+        return curPolymer
+    }
+
+    fun reactsWith(char1: Char, char2: Char): Boolean = abs(char1.minus(char2)) == 32
 }