2019. Day 5

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>

2019/day_05/day_05.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+)
+
+const (
+	opcodeAdd         = 1
+	opcodeMultiply    = 2
+	opcodeInput       = 3
+	opcodeOutput      = 4
+	opcodeJumpIfTrue  = 5
+	opcodeJumpIfFalse = 6
+	opcodeLessThan    = 7
+	opcodeEquals      = 8
+	opcodeHalt        = 99
+
+	paramModePosition  = 0
+	paramModeImmediate = 1
+)
+
+func readValues(fileName string) []int {
+	file, err := os.Open(fileName)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	var values []int
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		lineElements := strings.Split(scanner.Text(), ",")
+		for _, elem := range lineElements {
+			n, err := strconv.Atoi(elem)
+			if err != nil {
+				log.Fatalf("Cannot convert to int: %s\n", elem)
+			}
+			values = append(values, n)
+		}
+	}
+	return values
+}
+
+func runIntcode(values []int) {
+	instructionPointer := 0
+	for values[instructionPointer] != opcodeHalt {
+		instruction := values[instructionPointer]
+		opCode := instruction % 100
+
+		paramAddress := func(n int) int {
+			mode := (instruction % int(math.Pow10(n+2))) / int(math.Pow10(n+1))
+			switch mode {
+			case paramModeImmediate:
+				return instructionPointer + n
+			default:
+				return values[instructionPointer+n]
+			}
+		}
+
+		switch opCode {
+		case opcodeInput:
+			var input int
+			fmt.Print("Input: ")
+			_, err := fmt.Scanf("%d", &input)
+			if err != nil {
+				log.Fatalf("Cannot read integer from stdin: %s", err)
+			}
+			values[paramAddress(1)] = input
+			instructionPointer += 2
+		case opcodeOutput:
+			fmt.Printf("Output: %d\n", values[paramAddress(1)])
+			instructionPointer += 2
+		case opcodeAdd:
+			values[paramAddress(3)] = values[paramAddress(1)] + values[paramAddress(2)]
+			instructionPointer += 4
+		case opcodeMultiply:
+			values[paramAddress(3)] = values[paramAddress(1)] * values[paramAddress(2)]
+			instructionPointer += 4
+		case opcodeJumpIfTrue:
+			if values[paramAddress(1)] != 0 {
+				instructionPointer = values[paramAddress(2)]
+			} else {
+				instructionPointer += 3
+			}
+		case opcodeJumpIfFalse:
+			if values[paramAddress(1)] == 0 {
+				instructionPointer = values[paramAddress(2)]
+			} else {
+				instructionPointer += 3
+			}
+		case opcodeLessThan:
+			if values[paramAddress(1)] < values[paramAddress(2)] {
+				values[paramAddress(3)] = 1
+			} else {
+				values[paramAddress(3)] = 0
+			}
+			instructionPointer += 4
+		case opcodeEquals:
+			if values[paramAddress(1)] == values[paramAddress(2)] {
+				values[paramAddress(3)] = 1
+			} else {
+				values[paramAddress(3)] = 0
+			}
+			instructionPointer += 4
+		default:
+			log.Fatalf("Unknown opCode: %d\n", opCode)
+		}
+	}
+}
+
+func main() {
+	values := readValues("./input")
+	runIntcode(values)
+}