2024(4): solve puzzle 2

2024/4/README.md

@@ -72,3 +72,8 @@ M.M.M.M.M.
 In this example, an X-MAS appears 9 times.
 
 Flip the word search from the instructions back over to the word search side and try again. How many times does an X-MAS appear?
+
+
+Your puzzle answer was 1960.
+
+Both parts of this puzzle are complete! They provide two gold stars: **

2024/4/puzzle2.py

@@ -0,0 +1,30 @@
+verbose = False
+
+def x_mas_at(M, i: int, j: int) -> bool:
+	# NOTE: Checking i and j are not on the boundary is wise.
+
+	top_left  = \
+		M[i - 1][j - 1] == "M" and M[i + 1][j + 1] == "S" or \
+		M[i - 1][j - 1] == "S" and M[i + 1][j + 1] == "M"
+	top_right = \
+		M[i + 1][j - 1] == "M" and M[i - 1][j + 1] == "S" or \
+		M[i + 1][j - 1] == "S" and M[i - 1][j + 1] == "M"
+
+	return top_left and top_right
+
+if __name__ == "__main__":
+	result = 0
+	
+	with open("input", "r") as fp:
+		# Skip last line as it is empty.
+		full_string = fp.read().split("\n")[:-1]
+
+		x_mas_count = 0
+		
+		for i in range(1, len(full_string) - 1):
+			for j in range(1, len(full_string[0]) - 1):
+				if full_string[i][j] == "A":
+					if x_mas_at(full_string, i, j):
+						x_mas_count += 1
+
+	print(f"The sum of all horizontal X-MASs equals {x_mas_count}.")