solved(python): baekjoon 7578

Author: himitery

baekjoon/python/7578/__init__.py

@@ -0,0 +1,40 @@
+import sys
+
+read = lambda: sys.stdin.readline().rstrip()
+
+
+class Problem:
+    def __init__(self):
+        self.n = int(read())
+        self.a, self.b = list(map(int, read().split())), list(map(int, read().split()))
+
+        self.tree = [0] * (self.n + 1)
+
+    def solve(self) -> None:
+        pos_b, crossings = {machine_id: idx for idx, machine_id in enumerate(self.b)}, 0
+
+        for idx in range(self.n):
+            b_index = pos_b[self.a[idx]]
+            crossings += self.query(self.n - 1) - self.query(b_index)
+
+            self.update(b_index, 1)
+
+        print(crossings)
+
+    def update(self, idx: int, value: int) -> None:
+        idx += 1
+        while idx <= self.n:
+            self.tree[idx] += value
+            idx += idx & -idx
+
+    def query(self, idx: int) -> int:
+        idx, value = idx + 1, 0
+        while idx > 0:
+            value += self.tree[idx]
+            idx -= idx & -idx
+
+        return value
+
+
+if __name__ == "__main__":
+    Problem().solve()

baekjoon/python/7578/main.py

@@ -0,0 +1,12 @@
+[
+  {
+    "input": [
+      "5",
+      "132 392 311 351 231",
+      "392 351 132 311 231"
+    ],
+    "expected": [
+      "3"
+    ]
+  }
+]

baekjoon/python/7578/sample.json

@@ -0,0 +1,36 @@
+import json
+import os.path
+import unittest
+from io import StringIO
+from unittest.mock import patch
+
+from parameterized import parameterized
+
+from main import Problem
+
+
+def load_sample(filename: str):
+    path = os.path.join(os.path.dirname(os.path.abspath(__file__)), filename)
+
+    with open(path, "r") as file:
+        return [(case["input"], case["expected"]) for case in json.load(file)]
+
+
+class TestCase(unittest.TestCase):
+    @parameterized.expand(load_sample("sample.json"))
+    def test_case(self, case: str, expected: list[str]):
+        # When
+        with (
+            patch("sys.stdin.readline", side_effect=case),
+            patch("sys.stdout", new_callable=StringIO) as output,
+        ):
+            Problem().solve()
+
+            result = output.getvalue().rstrip()
+
+        # Then
+        self.assertEqual("\n".join(expected), result)
+
+
+if __name__ == "__main__":
+    unittest.main()