add and solve day 4 part 2

2024/day04.go

@@ -40,7 +40,51 @@ func (d Day4) Part1(r io.Reader) string {
 }
 
 func (d Day4) Part2(r io.Reader) string {
-	return ""
+	wordsearch := make([][]rune, 0)
+	s := bufio.NewScanner(r)
+	var sum int
+
+	for s.Scan() {
+		line := []rune(s.Text())
+		wordsearch = append(wordsearch, line)
+	}
+
+	s1 := make([]rune, 3)
+	s2 := make([]rune, 3)
+	for startx := range wordsearch {
+		for starty := range wordsearch[startx] {
+
+			toptobottom := [][]int{
+				{-1, -1},
+				{0, 0},
+				{1, 1},
+			}
+
+			for i, transpose := range toptobottom {
+				x, y := startx+transpose[0], starty+transpose[1]
+				s1[i] = runeAt(wordsearch, x, y)
+			}
+
+			bottomtotop := [][]int{
+				{-1, 1},
+				{0, 0},
+				{1, -1},
+			}
+
+			for i, transpose := range bottomtotop {
+				x, y := startx+transpose[0], starty+transpose[1]
+				s2[i] = runeAt(wordsearch, x, y)
+
+			}
+
+			if str1, str2 := string(s1), string(s2); (str1 == "SAM" || str1 == "MAS") && (str2 == "SAM" || str2 == "MAS") {
+				sum++
+			}
+
+		}
+	}
+
+	return printi(sum)
 }
 
 func runeAt(r [][]rune, x, y int) rune {

2024/puzzle_test.go

@@ -58,7 +58,7 @@ func TestPuzzles(t *testing.T) {
 		{
 			solver: Day4{},
 			ans1:   "18",
-			ans2:   "",
+			ans2:   "9",
 			inp1: `MMMSXXMASM
 MSAMXMSMSA
 AMXSXMAAMM
@@ -69,6 +69,16 @@ SMSMSASXSS
 SAXAMASAAA
 MAMMMXMMMM
 MXMXAXMASX`,
+			inp2: `.M.S......
+..A..MSMS.
+.M.S.MAA..
+..A.ASMSM.
+.M.S.M....
+..........
+S.S.S.S.S.
+.A.A.A.A..
+M.M.M.M.M.
+..........`,
 		},
 	}