2015-day12: missing having willy-nilly JSON.parse()

2015/day12/main.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	var ans int
+	if part == 1 {
+		ans = part1(util.ReadFile("./input.txt"))
+	} else {
+		ans = part2(util.ReadFile("./input.txt"))
+	}
+	fmt.Println("Output:", ans)
+}
+
+func part1(input string) int {
+	var totalSum int
+	var runningNum strings.Builder
+	for _, char := range input {
+		// got lucky on the input here
+		if regexp.MustCompile("[-0-9]").MatchString(string(char)) {
+			runningNum.WriteRune(char)
+		} else if runningNum.Len() != 0 {
+			totalSum += cast.ToInt(runningNum.String())
+			runningNum.Reset()
+		}
+	}
+
+	// this is for part 2 to handle ends of strings
+	if runningNum.Len() != 0 {
+		totalSum += cast.ToInt(runningNum.String())
+	}
+
+	return totalSum
+}
+
+// This solution leverages the error or nil that is returned from json.Marshal
+//
+// A full Go solution would requiring writing my own JSON parser
+// A much easier way would use javascript's JSON.parse and just do a dfs on it
+func part2(input string) int {
+	// if input does not have object braces or an instance of "red", just pass it through part1
+	if !regexp.MustCompile("[{}]").MatchString(input) ||
+		!regexp.MustCompile("red").MatchString(input) {
+		return part1(input)
+	}
+
+	// try to parse into an object if that's
+	var obj map[string]interface{}
+	err := json.Unmarshal([]byte(input), &obj)
+	// not a json object, assume it's an array
+	if err != nil {
+		// parse into an array
+		var arr []interface{}
+		err := json.Unmarshal([]byte(input), &arr)
+		if err != nil {
+			panic(err)
+		}
+
+		var arrayTotal int
+		for _, v := range arr {
+			// marshal each array element into a string, then pass it back into part2
+			str, err := json.Marshal(v)
+			if err != nil {
+				panic(err)
+			}
+			arrayTotal += part2(string(str))
+		}
+
+		return arrayTotal
+	}
+
+	// if any value in the object is "red" this object & its children RETURN ZERO
+	for _, v := range obj {
+		// have to convert interface into a string first
+		str, ok := v.(string)
+		if ok && str == "red" {
+			return 0
+		}
+	}
+
+	var total int
+	for _, v := range obj {
+		str, err := json.Marshal(v)
+		if err != nil {
+			panic(err)
+		}
+		total += part2(string(str))
+	}
+
+	return total
+}

2015/day12/main_test.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func Test_part1(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{"example", "[1,2,3]", 6},
+		{"example", "{\"a\":[-1,1]}", 0},
+		{"actual", util.ReadFile("input.txt"), 119433},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part1(tt.input); got != tt.want {
+				t.Errorf("part1() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_part2(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{"flat example 1", "[1,2,\"red\",5]", 8},
+		{"flat example 2", "5", 5},
+		{"actual", util.ReadFile("input.txt"), 68466},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part2(tt.input); got != tt.want {
+				t.Errorf("part2() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}