day2: solved part 2

Author: fxnn

day3/example.txt renamed to day3/example1.txt

@@ -0,0 +1,2 @@
+xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))
+

day3/example2.txt

@@ -17,12 +17,20 @@ func main() {
 		text += scanner.Text()
 	}
 
-	pattern := regexp.MustCompile(`mul\((\d+),(\d+)\)`)
+	pattern := regexp.MustCompile(`(do|don't)\(\)|mul\((\d+),(\d+)\)`)
 	result := 0
+	do := true
 	for _, match := range pattern.FindAllStringSubmatch(text, -1) {
-		n1 := util.Atoi(match[1])
-		n2 := util.Atoi(match[2])
-		result += n1 * n2
+		fmt.Printf("%v\n", match)
+		if match[1] == "do" {
+			do = true
+		} else if match[1] == "don't" {
+			do = false
+		} else if do {
+			n1 := util.Atoi(match[2])
+			n2 := util.Atoi(match[3])
+			result += n1 * n2
+		}
 	}
 
 	fmt.Printf("result: %d\n", result)