day02 solution

2018/day02/part2/main.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"adventofcode/util"
+	"fmt"
+	"strings"
+)
+
+// brute force it...
+// assume only one valid answer
+func main() {
+	input := util.ReadFile("../input.txt")
+	lines := strings.Split(input, "\n")
+	for i := 0; i < len(lines); i++ {
+		for j := i + 1; j < len(lines); j++ {
+			if sameChars := getSameCharacters(lines[i], lines[j]); sameChars != "" {
+				fmt.Println("common letters are", sameChars)
+				return
+			}
+		}
+	}
+}
+
+func getSameCharacters(str1, str2 string) string {
+	var mismatchSeen bool
+	var sameChars string
+	for i := 0; i < len(str1); i++ {
+		if str1[i] == str2[i] {
+			sameChars += string(str1[i])
+		} else if mismatchSeen {
+			// if a mismatch has already been seen, then it's 2 characters off
+			// return an empty string
+			return ""
+		} else {
+			mismatchSeen = true
+		}
+	}
+	return sameChars
+}