solved(python): baekjoon 1967

Author: himitery

baekjoon/python/1967/__init__.py

@@ -0,0 +1,49 @@
+import heapq
+import math
+import sys
+
+from collections import defaultdict
+
+read = lambda: sys.stdin.readline().rstrip()
+
+
+class Problem:
+    def __init__(self):
+        self.n = int(read())
+
+        self.graph = defaultdict(list)
+        for src, dest, distance in [map(int, read().split()) for _ in range(self.n - 1)]:
+            self.graph[src].append((dest, distance))
+            self.graph[dest].append((src, distance))
+
+    def solve(self) -> None:
+        if self.n == 1:
+            print(0)
+            return
+
+        distances, target = self.dijkstra(1), (0, 0)
+        for idx, distance in enumerate(distances):
+            if distance > target[0]:
+                target = (distance, idx + 1)
+
+        print(max(self.dijkstra(target[1])))
+
+    def dijkstra(self, start_vertex: int) -> list[int]:
+        queue, distances = [(0, start_vertex)], [0 if idx == start_vertex else math.inf for idx in range(self.n + 1)]
+
+        while queue:
+            current_distance, current_vertex = heapq.heappop(queue)
+            if current_distance > distances[current_vertex]:
+                continue
+
+            for next_vertex, distance in self.graph[current_vertex]:
+                next_distance = current_distance + distance
+                if next_distance < distances[next_vertex]:
+                    distances[next_vertex] = next_distance
+                    heapq.heappush(queue, (next_distance, next_vertex))
+
+        return list(map(int, distances[1:]))
+
+
+if __name__ == "__main__":
+    Problem().solve()

baekjoon/python/1967/main.py

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+[
+  {
+    "input": [
+      "12",
+      "1 2 3",
+      "1 3 2",
+      "2 4 5",
+      "3 5 11",
+      "3 6 9",
+      "4 7 1",
+      "4 8 7",
+      "5 9 15",
+      "5 10 4",
+      "6 11 6",
+      "6 12 10"
+    ],
+    "expected": [
+      "45"
+    ]
+  }
+]

baekjoon/python/1967/sample.json

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+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()