Day 4 Part 1

day-02/computer.nim

@@ -0,0 +1,69 @@
+import sequtils, strutils
+
+type
+  Program* = seq[int]
+  Input* = object
+    noun*: int
+    verb*: int
+  Computer* = ref object
+    source: Program     # Original program code without modifications
+    program*: Program   # The computers program in memory
+    ic*: int            # The instruction counter
+
+  StopExecution = object of Exception
+  ## This will be raised when the ending opcode is reached
+  
+proc set(cp: Computer, address, value: int): void = 
+  cp.program[address] = value
+
+proc get(cp: Computer, address: int): int = 
+  cp.program[address]
+
+proc add(cp: Computer, param1, param2, param3: int): void =
+  cp.set(param3, (cp.get(param1) + cp.get(param2)))
+
+proc mul(cp: Computer, param1, param2, param3: int): void =
+  cp.set(param3, (cp.get(param1) * cp.get(param2)))
+
+proc newComputer*(sourceFile: string): Computer =  
+  var file = readFile("input.txt");
+  file.stripLineEnd
+  let source = map(split(file, ','), parseInt)  
+  result = Computer(source: source, ic: 0)
+
+proc reset*(cp: Computer, input: Input): void =
+  ## Reset instruction pointer, program code and input values
+  cp.program = cp.source
+  cp.ic = 0
+  cp.set(1, input.noun)
+  cp.set(2, input.verb)
+
+proc process(cp: Computer): void = 
+  let opCode = cp.get(cp.ic)
+  if opCode == 99:   # End Execution
+    raise newException(StopExecution, "Program ended")
+  if opCode == 1:    # Addition
+    cp.add(cp.get(cp.ic+1), cp.get(cp.ic+2), cp.get(cp.ic+3))
+  if opCode == 2:    # Multiplication
+    cp.mul(cp.get(cp.ic+1), cp.get(cp.ic+2), cp.get(cp.ic+3))
+  cp.ic += 4
+
+proc run*(cp: Computer): int =
+  ## Runs the program loaded in memory until complete
+  try:
+    while true:
+      cp.process
+  except StopExecution:
+    return cp.get(0)
+  return -1   # Something went wrong
+
+proc findInputFor*(cp: Computer, target: int): Input =
+  ## Finds fitting inputs to produce the desired output
+  ## Stops at the first match
+  for noun in 0 .. 99:
+    for verb in 0 .. 99:
+      let input = Input(noun: noun, verb: verb)
+      cp.reset(input)
+      var output = cp.run
+      if output == target:
+        return input

day-02/input.txt

@@ -0,0 +1 @@
+1,0,0,3,1,1,2,3,1,3,4,3,1,5,0,3,2,1,6,19,1,5,19,23,1,23,6,27,1,5,27,31,1,31,6,35,1,9,35,39,2,10,39,43,1,43,6,47,2,6,47,51,1,5,51,55,1,55,13,59,1,59,10,63,2,10,63,67,1,9,67,71,2,6,71,75,1,5,75,79,2,79,13,83,1,83,5,87,1,87,9,91,1,5,91,95,1,5,95,99,1,99,13,103,1,10,103,107,1,107,9,111,1,6,111,115,2,115,13,119,1,10,119,123,2,123,6,127,1,5,127,131,1,5,131,135,1,135,6,139,2,139,10,143,2,143,9,147,1,147,6,151,1,151,13,155,2,155,9,159,1,6,159,163,1,5,163,167,1,5,167,171,1,10,171,175,1,13,175,179,1,179,2,183,1,9,183,0,99,2,14,0,0

day-02/main.nim

@@ -0,0 +1,19 @@
+import computer
+
+proc solvePart1(): void = 
+  var 
+    cp = newComputer("input.txt")
+    input = Input(noun: 12, verb: 2)
+  cp.reset(input)
+  let result = cp.run
+  echo "Result for Part 1: ", result
+
+proc solvePart2(): void =
+  var 
+    target = 19690720
+    cp = newComputer("input.txt")
+    inputs = cp.findInputFor(target)
+  echo "result for Part 2: ", 100 * inputs.noun + inputs.verb
+
+solvePart1()
+solvePart2()