solved(python): baekjoon 11400

Author: himitery

baekjoon/python/11400/__init__.py

@@ -0,0 +1,70 @@
+import sys
+from collections import defaultdict, deque
+
+read = lambda: sys.stdin.readline().rstrip()
+
+
+class Problem:
+    def __init__(self) -> None:
+        self.v, self.e = map(int, read().split())
+
+        self.graph = defaultdict(list[int])
+        for x, y in [map(int, read().split()) for _ in range(self.e)]:
+            self.graph[x].append(y)
+            self.graph[y].append(x)
+
+    def solve(self) -> None:
+        discovered, low, bridges, order = (
+            [-1] * (self.v + 1),
+            [-1] * (self.v + 1),
+            [],
+            0,
+        )
+
+        for node in range(1, self.v + 1):
+            if discovered[node] == -1:
+                order = self.find_bridges(node, discovered, low, bridges, order)
+
+        print(len(bridges))
+        for bridge in sorted(bridges):
+            print(*bridge)
+
+    def find_bridges(
+        self,
+        start_node: int,
+        discovered: list[int],
+        low: list[int],
+        bridges: list[list[int]],
+        order: int,
+    ) -> int:
+        stack = deque([(start_node, 0, iter(self.graph[start_node]))])
+
+        while stack:
+            current_node, parent, neighbors = stack[-1]
+
+            if discovered[current_node] == -1:
+                order += 1
+                discovered[current_node] = low[current_node] = order
+
+            for neighbor in neighbors:
+                if neighbor == parent:
+                    continue
+
+                if discovered[neighbor] != -1:
+                    low[current_node] = min(low[current_node], discovered[neighbor])
+                else:
+                    stack.append((neighbor, current_node, iter(self.graph[neighbor])))
+                    break
+            else:
+                popped_node, parent_node, _ = stack.pop()
+
+                if parent_node != 0:
+                    low[parent_node] = min(low[parent_node], low[popped_node])
+                    if low[popped_node] > discovered[parent_node]:
+                        bridges.append(sorted([parent_node, popped_node]))
+
+        return order
+
+
+if __name__ == "__main__":
+    Problem().solve()

baekjoon/python/11400/main.py

@@ -0,0 +1,20 @@
+[
+  {
+    "input": [
+      "7 8",
+      "1 4",
+      "4 5",
+      "5 1",
+      "1 6",
+      "6 7",
+      "2 7",
+      "7 3",
+      "2 3"
+    ],
+    "expected": [
+      "2",
+      "1 6",
+      "6 7"
+    ]
+  }
+]

baekjoon/python/11400/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()