Combine AoC Repos

2016/day09/main.go

@@ -0,0 +1,124 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"regexp"
+	"strconv"
+)
+
+var re *regexp.Regexp
+
+func main() {
+	var input []byte
+	var noDecompress bool
+	var printSize bool
+	if len(os.Args) > 1 {
+		for i := 1; i < len(os.Args); i++ {
+			if os.Args[i][0] != '-' {
+				// Assume it's a filename
+				// Read from the given filename
+				input = fileToByteSlice(os.Args[1])
+			} else {
+				switch os.Args[i] {
+				case "-size":
+					printSize = true
+				case "-dry":
+					// -dry implies printSize
+					printSize = true
+					noDecompress = true
+				}
+			}
+		}
+	}
+	if len(input) == 0 {
+		// Must be stdin
+		input = stdinToByteSlice()
+	}
+	input = bytes.TrimSpace(input)
+	// re matches compression markers and submatches the values we care about
+	re = regexp.MustCompile(`\((\d*)x(\d*)\)`)
+
+	if noDecompress {
+		cnt := depthDecompressLength(input)
+		fmt.Println("Total Decompressed Bytes:", cnt)
+		os.Exit(0)
+	}
+	output := depthDecompress(input)
+	fmt.Println(string(output))
+	if printSize {
+		fmt.Println("Total Decompressed Bytes:", len(output))
+	}
+}
+
+// depthDecompressLength counts how many uncompressed bytes are
+// in the byte slice by unravelling the compression levels
+// recursively
+func depthDecompressLength(cmp []byte) uint64 {
+	mrkParts := re.FindStringSubmatch(string(cmp))
+	if len(mrkParts) < 3 {
+		// No compressionmarker, just return cmp length
+		return uint64(len(cmp))
+	}
+	marker, mrkBytes, mrkDupe := []byte(mrkParts[0]), atoi(mrkParts[1]), atoi(mrkParts[2])
+	mrkPos := bytes.Index(cmp, marker)
+	if mrkPos > 0 {
+		cmp = cmp[mrkPos:]
+	}
+	recurBytes := bytes.TrimPrefix(cmp, marker)[:mrkBytes]
+	remainder := bytes.TrimPrefix(cmp, append(marker, recurBytes...))
+	return uint64(mrkPos) + (depthDecompressLength(recurBytes) * uint64(mrkDupe)) + depthDecompressLength(remainder)
+}
+
+func depthDecompress(cmp []byte) []byte {
+	mrkParts := re.FindStringSubmatch(string(cmp))
+	if len(mrkParts) < 3 {
+		// No compression marker, just return cmp length
+		return cmp
+	}
+	marker, mrkBytes, mrkDupe := []byte(mrkParts[0]), atoi(mrkParts[1]), atoi(mrkParts[2])
+	mrkPos := bytes.Index(cmp, marker)
+	var ret []byte
+	if mrkPos > 0 {
+		ret = cmp[:mrkPos]
+		cmp = cmp[mrkPos:]
+	}
+	recurBytes := bytes.TrimPrefix(cmp, marker)[:mrkBytes]
+	remainder := bytes.TrimPrefix(cmp, append(marker, recurBytes...))
+
+	ret = append(ret, bytes.Repeat(depthDecompress(recurBytes), mrkDupe)...)
+	return append(ret, depthDecompress(remainder)...)
+}
+
+func fileToByteSlice(fn string) []byte {
+	var c []byte
+	var err error
+	c, err = ioutil.ReadFile(fn)
+	if err != nil {
+		fmt.Println("Unable to read file: " + fn)
+		os.Exit(1)
+	}
+	return c
+}
+
+func stdinToByteSlice() []byte {
+	var input string
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		input += scanner.Text()
+	}
+	return []byte(input)
+}
+
+func atoi(i string) int {
+	var ret int
+	var err error
+	if ret, err = strconv.Atoi(i); err != nil {
+		log.Fatal("Invalid Atoi")
+	}
+	return ret
+}