solved(python): baekjoon 15681

Author: himitery

baekjoon/python/15681/__init__.py

@@ -0,0 +1,45 @@
+import sys
+from collections import defaultdict, deque
+
+read = lambda: sys.stdin.readline().rstrip()
+
+
+class Problem:
+    def __init__(self):
+        self.n, self.r, self.q = map(int, read().split())
+
+        self.edges = defaultdict(list)
+        for _ in range(self.n - 1):
+            x, y = map(int, read().split())
+            self.edges[x].append(y)
+            self.edges[y].append(x)
+
+        self.queries = [int(read()) for _ in range(self.q)]
+
+    def solve(self) -> None:
+        children = self.find_children(self.r)
+
+        for query in self.queries:
+            print(children[query])
+
+    def find_children(self, num: int) -> list[int]:
+        stack, cached = deque([(num, -1)]), []
+
+        while stack:
+            node, head = stack.pop()
+            cached.append((node, head))
+
+            for child in self.edges[node]:
+                if child != head:
+                    stack.append((child, node))
+
+        children = [1] * (self.n + 1)
+        for node, head in reversed(cached):
+            if head != -1:
+                children[head] += children[node]
+
+        return children
+
+
+if __name__ == "__main__":
+    Problem().solve()

baekjoon/python/15681/main.py

@@ -0,0 +1,44 @@
+[
+  {
+    "input": [
+      "9 5 3",
+      "1 3",
+      "4 3",
+      "5 4",
+      "5 6",
+      "6 7",
+      "2 3",
+      "9 6",
+      "6 8",
+      "5",
+      "4",
+      "8"
+    ],
+    "expected": [
+      "9",
+      "4",
+      "1"
+    ]
+  },
+  {
+    "input": [
+      "9 1 3",
+      "1 3",
+      "4 3",
+      "5 4",
+      "5 6",
+      "6 7",
+      "2 3",
+      "9 6",
+      "6 8",
+      "1",
+      "9",
+      "6"
+    ],
+    "expected": [
+      "9",
+      "1",
+      "4"
+    ]
+  }
+]

baekjoon/python/15681/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()