diff --git a/day19/day.go b/day19/day.go
new file mode 100644
index 0000000..15d9700
--- /dev/null
+++ b/day19/day.go
@@ -0,0 +1,104 @@
+package day19
+
+import (
+	"strings"
+	"tools"
+)
+
+func Part1(puzzle tools.AoCPuzzle) interface{} {
+	input := puzzle.GetInputArray()
+	molecule := input[len(input)-1]
+	replacementStrings := input[:len(input)-2]
+	outcomes := tools.NewSet()
+
+	for _, line := range replacementStrings {
+		parts := strings.Split(line, " => ")
+		doubleChar := len(parts[0]) == 2
+		var result string
+		for i, c := range molecule {
+			if doubleChar && i == len(molecule)-1 {
+				break
+			}
+			if doubleChar {
+				if byte(c) == parts[0][0] && molecule[i+1] == parts[0][1] {
+					result = molecule[:i] + parts[1]
+					if i < len(molecule)-2 {
+						result += molecule[i+2:]
+					}
+					outcomes.Add(result)
+				}
+			} else {
+				if string(c) == parts[0] {
+					result = molecule[:i] + parts[1]
+					if i < len(molecule)-1 {
+						result += molecule[i+1:]
+					}
+					outcomes.Add(result)
+				}
+			}
+		}
+	}
+
+	return len(outcomes)
+}
+
+func getPossibleTransformations(from tools.Set, replacments map[string]tools.Set, maxLen int) tools.Set {
+	returnSet := tools.NewSet()
+	var result string
+
+	for interfaceMolecule := range from {
+		currentMolecule := interfaceMolecule.(string)
+		for i := range currentMolecule {
+			if transSet, ok := replacments[string(currentMolecule[i])]; ok {
+				for replacement := range transSet {
+					result = currentMolecule[:i] + replacement.(string)
+					if i < len(currentMolecule)-1 {
+						result += currentMolecule[i+1:]
+					}
+					if len(result) <= maxLen {
+						returnSet.Add(result)
+					}
+				}
+			}
+			if i < len(currentMolecule)-1 {
+				if transSet, ok := replacments[currentMolecule[i:i+2]]; ok {
+					for replacment := range transSet {
+						result = currentMolecule[:i] + replacment.(string)
+						if i < len(currentMolecule)-2 {
+							result += currentMolecule[i+2:]
+						}
+						if len(result) <= maxLen {
+							returnSet.Add(result)
+						}
+					}
+				}
+			}
+		}
+	}
+
+	return returnSet
+}
+
+func Part2(puzzle tools.AoCPuzzle) interface{} {
+	input := puzzle.GetInputArray()
+	molecule := input[len(input)-1]
+	replacementStrings := input[:len(input)-2]
+	replacements := make(map[string]tools.Set)
+	for _, line := range replacementStrings {
+		parts := strings.Split(line, " => ")
+		if _, ok := replacements[parts[0]]; !ok {
+			replacements[parts[0]] = tools.NewSet()
+		}
+		replacements[parts[0]].Add(parts[1])
+	}
+
+	currentMolecules := tools.NewSet()
+	currentMolecules.Add("e")
+	transformCount := 0
+	for !currentMolecules.Contains(molecule) {
+		transformCount++
+		currentMolecules = getPossibleTransformations(currentMolecules, replacements, len(molecule))
+	}
+
+	return transformCount
+}
diff --git a/inputs/19 b/inputs/19
new file mode 100644
index 0000000..e3001ec
--- /dev/null
+++ b/inputs/19
@@ -0,0 +1,45 @@
+Al => ThF
+Al => ThRnFAr
+B => BCa
+B => TiB
+B => TiRnFAr
+Ca => CaCa
+Ca => PB
+Ca => PRnFAr
+Ca => SiRnFYFAr
+Ca => SiRnMgAr
+Ca => SiTh
+F => CaF
+F => PMg
+F => SiAl
+H => CRnAlAr
+H => CRnFYFYFAr
+H => CRnFYMgAr
+H => CRnMgYFAr
+H => HCa
+H => NRnFYFAr
+H => NRnMgAr
+H => NTh
+H => OB
+H => ORnFAr
+Mg => BF
+Mg => TiMg
+N => CRnFAr
+N => HSi
+O => CRnFYFAr
+O => CRnMgAr
+O => HP
+O => NRnFAr
+O => OTi
+P => CaP
+P => PTi
+P => SiRnFAr
+Si => CaSi
+Th => ThCa
+Ti => BP
+Ti => TiTi
+e => HF
+e => NAl
+e => OMg
+
+CRnSiRnCaPTiMgYCaPTiRnFArSiThFArCaSiThSiThPBCaCaSiRnSiRnTiTiMgArPBCaPMgYPTiRnFArFArCaSiRnBPMgArPRnCaPTiRnFArCaSiThCaCaFArPBCaCaPTiTiRnFArCaSiRnSiAlYSiThRnFArArCaSiRnBFArCaCaSiRnSiThCaCaCaFYCaPTiBCaSiThCaSiThPMgArSiRnCaPBFYCaCaFArCaCaCaCaSiThCaSiRnPRnFArPBSiThPRnFArSiRnMgArCaFYFArCaSiRnSiAlArTiTiTiTiTiTiTiRnPMgArPTiTiTiBSiRnSiAlArTiTiRnPMgArCaFYBPBPTiRnSiRnMgArSiThCaFArCaSiThFArPRnFArCaSiRnTiBSiThSiRnSiAlYCaFArPRnFArSiThCaFArCaCaSiThCaCaCaSiRnPRnCaFArFYPMgArCaPBCaPBSiRnFYPBCaFArCaSiAl
\ No newline at end of file
diff --git a/inputs/19_test b/inputs/19_test
new file mode 100644
index 0000000..7617b7a
--- /dev/null
+++ b/inputs/19_test
@@ -0,0 +1,7 @@
+e => H
+e => Oi
+H => HOi
+H => OiH
+Oi => HH
+
+HOiHOiHOi
\ No newline at end of file
diff --git a/main.go b/main.go
index e1a04f8..36747d0 100644
--- a/main.go
+++ b/main.go
@@ -19,6 +19,7 @@ import (
 	"aoc2015/day16"
 	"aoc2015/day17"
 	"aoc2015/day18"
+	"aoc2015/day19"
 	"flag"
 	"fmt"
 	"os"
@@ -54,6 +55,7 @@ func initDayFunctions() {
 		16: {1: day16.Part1, 2: day16.Part2},
 		17: {1: day17.Part1, 2: day17.Part2},
 		18: {1: day18.Part1, 2: day18.Part2},
+		19: {1: day19.Part1, 2: day19.Part2},
 	}
 }