From f9b2cbf69a74172d266de6dfff6df9fdaa564c1f Mon Sep 17 00:00:00 2001
From: stanislas <stanislas@jouf.fr>
Date: Wed, 4 Dec 2024 16:14:01 +0100
Subject: [PATCH] day 4 - part 2

---
 src/aoc_2024/day4/part2.py        | 75 +++++++++++++++++++++++++++++++
 tests/aoc_2024/day4/test_part2.py | 33 ++++++++++++++
 2 files changed, 108 insertions(+)
 create mode 100644 src/aoc_2024/day4/part2.py
 create mode 100644 tests/aoc_2024/day4/test_part2.py

diff --git a/src/aoc_2024/day4/part2.py b/src/aoc_2024/day4/part2.py
new file mode 100644
index 0000000..aed5b56
--- /dev/null
+++ b/src/aoc_2024/day4/part2.py
@@ -0,0 +1,75 @@
+from pathlib import Path
+
+import numpy as np
+
+
+def is_diagonal_forwards_downwards(data, i, j):
+    if data[i - 1, j - 1] == "M":
+        if data[i + 1, j + 1] == "S":
+            return True
+    return False
+
+
+def is_diagonal_forwards_upwards(data, i, j):
+    if data[i + 1, j - 1] == "M":
+        if data[i - 1, j + 1] == "S":
+            return True
+    return False
+
+
+def is_diagonal_backwards_upwards(data, i, j):
+    if data[i + 1, j + 1] == "M":
+        if data[i - 1, j - 1] == "S":
+            return True
+    return False
+
+
+def is_diagonal_backwards_downwards(data, i, j):
+    if data[i - 1, j + 1] == "M":
+        if data[i + 1, j - 1] == "S":
+            return True
+    return False
+
+
+def is_diagonal1(data, i, j):
+    return is_diagonal_forwards_downwards(data, i, j) or is_diagonal_backwards_upwards(
+        data, i, j
+    )
+
+
+def is_diagonal2(data, i, j):
+    return is_diagonal_backwards_downwards(data, i, j) or is_diagonal_forwards_upwards(
+        data, i, j
+    )
+
+
+def find_x_mas(data: np.array):
+    score = 0
+    for i in range(1, data.shape[0] - 1):
+        for j in range(1, data.shape[1] - 1):
+            if data[i, j] == "A":
+                if is_diagonal1(data, i, j) and is_diagonal2(data, i, j):
+                    score += 1
+
+    return score
+
+
+def main(file: Path) -> int:
+    data_str = file.read_text()
+    x_axis_size = data_str.find("\n")
+    y_axis_size = data_str.count("\n") + 1
+    data = np.full((x_axis_size, y_axis_size), "")
+    i, j = 0, 0
+    for character in data_str:
+        if character != "\n":
+            data[i, j] = character
+            j += 1
+        else:
+            i += 1
+            j = 0
+    return find_x_mas(data)
+
+
+if __name__ == "__main__":
+    input_file = Path(__file__).parent / "input-data"
+    print(main(input_file))
diff --git a/tests/aoc_2024/day4/test_part2.py b/tests/aoc_2024/day4/test_part2.py
new file mode 100644
index 0000000..b48876b
--- /dev/null
+++ b/tests/aoc_2024/day4/test_part2.py
@@ -0,0 +1,33 @@
+from pathlib import Path
+
+from aoc_2024.day4 import part2
+
+import numpy as np
+
+
+def test_find_all():
+    data_str = """MMMSXXMASM
+MSAMXMSMSA
+AMXSXMAAMM
+MSAMASMSMX
+XMASAMXAMM
+XXAMMXXAMA
+SMSMSASXSS
+SAXAMASAAA
+MAMMMXMMMM
+MXMXAXMASX"""
+    data = np.full((10, 10), "")
+    i, j = 0, 0
+    for character in data_str:
+        if character != "\n":
+            data[i, j] = character
+            j += 1
+        else:
+            i += 1
+            j = 0
+    assert part2.find_x_mas(data) == 9
+
+
+def test_main():
+    data_file = Path(__file__).parent / "test-data"
+    assert part2.main(data_file) == 9