solve day 3 part 2

2024/day03.go

@@ -24,5 +24,26 @@ func (d Day3) Part1(r io.Reader) string {
 }
 
 func (d Day3) Part2(r io.Reader) string {
-	return ""
+	var bd strings.Builder
+	var sum int
+	io.Copy(&bd, r)
+
+	re := regexp.MustCompile(`mul\((\d{1,3}),(\d{1,3})\)|do\(\)|don\'t\(\)`)
+
+	matches := re.FindAllStringSubmatch(bd.String(), -1)
+
+	var skip bool
+	for _, match := range matches {
+		switch match[0] {
+		case "do()":
+			skip = false
+		case "don't()":
+			skip = true
+		default:
+			if !skip {
+				sum += atoi(match[1]) * atoi(match[2])
+			}
+		}
+	}
+	return printi(sum)
 }

2024/puzzle_test.go

@@ -21,14 +21,15 @@ func TestPuzzles(t *testing.T) {
 		solver puzzle
 		ans1   string
 		ans2   string
-		input  string
+		inp1   string
+		inp2   string
 	}{
 
 		{
 			solver: Day1{},
 			ans1:   "11",
 			ans2:   "31",
-			input: `3   4
+			inp1: `3   4
 4   3
 2   5
 1   3
@@ -39,7 +40,7 @@ func TestPuzzles(t *testing.T) {
 			solver: Day2{},
 			ans1:   "2",
 			ans2:   "4",
-			input: `7 6 4 2 1
+			inp1: `7 6 4 2 1
 1 2 7 8 9
 9 7 6 2 1
 1 3 2 4 5
@@ -49,15 +50,19 @@ func TestPuzzles(t *testing.T) {
 		{
 			solver: Day3{},
 			ans1:   "161",
-			ans2:   "",
-			input:  "xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))",
+			ans2:   "48",
+			inp1:   "xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))",
+			inp2:   "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))",
 		},
 	}
 
 	for i, tt := range tests {
 		name := fmt.Sprintf("Day%d", i+1)
 		t.Run(name, func(t *testing.T) {
-			p1, p2 := dup(tt.input)
+			p1, p2 := dup(tt.inp1)
+			if tt.inp2 != "" {
+				p2 = strings.NewReader(tt.inp2)
+			}
 			if got := tt.solver.Part1(p1); got != tt.ans1 {
 				t.Errorf("Part 1 = %s; expected %s", got, tt.ans1)
 			}