solved(python): baekjoon 1865

Author: himitery

baekjoon/python/1865/__init__.py

@@ -0,0 +1,51 @@
+import math
+import sys
+
+read = lambda: sys.stdin.readline().rstrip()
+
+
+class Problem:
+    def __init__(self):
+        self.n, self.m, self.w = map(int, read().split())
+        self.graph, self.visited = [], set()
+
+        for _ in range(self.m):
+            src, dest, time = map(int, read().split())
+            self.graph.append((src - 1, dest - 1, time))
+            self.graph.append((dest - 1, src - 1, time))
+
+        for _ in range(self.w):
+            src, dest, time = map(int, read().split())
+            self.graph.append((src - 1, dest - 1, -time))
+
+    def solve(self) -> None:
+        for node in range(self.n):
+            if node not in self.visited and self.bellman_ford(node):
+                print("YES")
+                return
+
+        print("NO")
+
+    def bellman_ford(self, node: int) -> bool:
+        distances = [0 if node == idx else math.inf for idx in range(self.n)]
+
+        for idx in range(self.n):
+            updated = False
+            for src, dest, time in self.graph:
+                if distances[src] != math.inf and distances[dest] > distances[src] + time:
+                    distances[dest] = distances[src] + time
+                    self.visited |= {src, dest}
+                    updated = True
+
+                    if idx == self.n - 1:
+                        return True
+
+            if not updated:
+                return False
+
+        return False
+
+
+if __name__ == "__main__":
+    for _ in range(int(read())):
+        Problem().solve()

baekjoon/python/1865/main.py

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+[
+  {
+    "input": [
+      "2",
+      "3 3 1",
+      "1 2 2",
+      "1 3 4",
+      "2 3 1",
+      "3 1 3",
+      "3 2 1",
+      "1 2 3",
+      "2 3 4",
+      "3 1 8"
+    ],
+    "expected": [
+      "NO",
+      "YES"
+    ]
+  }
+]

baekjoon/python/1865/sample.json

@@ -0,0 +1,38 @@
+import json
+import os.path
+import sys
+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,
+        ):
+            for _ in range(int(sys.stdin.readline().rstrip())):
+                Problem().solve()
+
+            result = output.getvalue().rstrip()
+
+        # Then
+        self.assertEqual("\n".join(expected), result)
+
+
+if __name__ == "__main__":
+    unittest.main()