solved(python): baekjoon 1948

Author: himitery

baekjoon/python/1948/__init__.py

@@ -0,0 +1,64 @@
+import sys
+from collections import defaultdict, deque
+
+read = lambda: sys.stdin.readline().rstrip()
+
+
+class Problem:
+    def __init__(self):
+        self.n, self.m = int(read()), int(read())
+        self.graph, self.reverse_graph, self.in_degree = (
+            defaultdict(list[tuple[int, int]]),
+            defaultdict(list[tuple[int, int]]),
+            [0 for _ in range(self.n)],
+        )
+
+        for src, dest, time in [map(int, read().split()) for _ in range(self.m)]:
+            self.graph[src - 1].append((dest - 1, time))
+            self.reverse_graph[dest - 1].append((src - 1, time))
+            self.in_degree[dest - 1] += 1
+
+        self.src, self.dest = map(lambda x: int(x) - 1, read().split())
+
+    def solve(self) -> None:
+        costs = self.topological_sort()
+
+        print(costs[self.dest])
+        print(self.count_critical_paths(costs))
+
+    def topological_sort(self) -> list[int]:
+        queue, costs = deque([self.src]), [0 for _ in range(self.n)]
+
+        while queue:
+            node = queue.popleft()
+
+            for next_node, next_time in self.graph[node]:
+                if costs[next_node] < costs[node] + next_time:
+                    costs[next_node] = costs[node] + next_time
+
+                self.in_degree[next_node] -= 1
+                if self.in_degree[next_node] == 0:
+                    queue.append(next_node)
+
+        return costs
+
+    def count_critical_paths(self, costs: list[int]) -> int:
+        queue, visited, count = deque([self.dest]), {self.dest}, 0
+
+        while queue:
+            node = queue.popleft()
+
+            for prev, cost in self.reverse_graph[node]:
+                if costs[prev] + cost != costs[node]:
+                    continue
+
+                count += 1
+                if prev not in visited:
+                    visited.add(prev)
+                    queue.append(prev)
+
+        return count
+
+
+if __name__ == "__main__":
+    Problem().solve()

baekjoon/python/1948/main.py

@@ -0,0 +1,22 @@
+[
+  {
+    "input": [
+      "7",
+      "9",
+      "1 2 4",
+      "1 3 2",
+      "1 4 3",
+      "2 6 3",
+      "2 7 5",
+      "3 5 1",
+      "4 6 4",
+      "5 6 2",
+      "6 7 5",
+      "1 7"
+    ],
+    "expected": [
+      "12",
+      "5"
+    ]
+  }
+]

baekjoon/python/1948/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()