clanker: veet-hard-problems (run)

problems/hard/task-scheduler/solution.py

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+"""
+Task Scheduler
+
+You're building a CI/CD pipeline orchestrator. Given a set of build tasks
+with durations and dependency requirements, determine the minimum total
+time to complete all tasks when independent tasks can run in parallel.
+Also detect if the dependency graph contains a cycle (making the build
+impossible).
+
+Each task is represented as (name, duration, dependencies) where
+dependencies is a list of task names that must complete before this
+task can start.
+
+Example 1:
+    Input: tasks = [("compile", 3, []), ("test", 5, ["compile"]), ("lint", 2, []), ("deploy", 1, ["test", "lint"])]
+    Output: (9, ["compile", "test", "deploy"])
+    Explanation: compile(3) -> test(5) -> deploy(1) = 9. lint(2) runs in parallel and finishes before deploy starts. The critical path is compile -> test -> deploy.
+
+Example 2:
+    Input: tasks = [("A", 2, ["B"]), ("B", 3, ["A"])]
+    Output: (-1, [])
+    Explanation: Circular dependency between A and B makes execution impossible.
+
+Example 3:
+    Input: tasks = [("X", 4, []), ("Y", 4, []), ("Z", 1, ["X", "Y"])]
+    Output: (5, ["X", "Z"])
+    Explanation: X and Y run in parallel (both take 4). Z waits for both, then takes 1. Critical path is X(4) -> Z(1) = 5 (or equivalently Y -> Z). Return either.
+
+Constraints:
+    - Task names are unique non-empty strings
+    - Durations are positive integers (>= 1)
+    - Dependencies reference other task names in the list
+    - Return (-1, []) if a cycle exists
+    - The critical path is the longest path through the dependency graph
+    - If multiple critical paths have the same length, return any one
+    - The critical path list is ordered from first task to last
+    - All tasks must be completed; the answer is the makespan
+"""
+
+
+def schedule_tasks(
+    tasks: list[tuple[str, int, list[str]]],
+) -> tuple[int, list[str]]:
+    """Return (min_total_time, critical_path) or (-1, []) if cycle exists."""
+    pass  # Your implementation here

problems/hard/task-scheduler/tests.py

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+"""Tests for task-scheduler."""
+import pytest
+from solution import schedule_tasks
+
+
+class TestBasicCases:
+    """Test basic functionality with typical inputs."""
+
+    def test_example_one(self):
+        """Test first example from problem description."""
+        tasks = [("compile", 3, []), ("test", 5, ["compile"]), ("lint", 2, []), ("deploy", 1, ["test", "lint"])]
+        assert schedule_tasks(tasks) == (9, ["compile", "test", "deploy"])
+
+    def test_example_two_cycle(self):
+        """Test second example with circular dependency."""
+        tasks = [("A", 2, ["B"]), ("B", 3, ["A"])]
+        assert schedule_tasks(tasks) == (-1, [])
+
+    def test_example_three_parallel(self):
+        """Test parallel tasks with shared dependency."""
+        tasks = [("X", 4, []), ("Y", 4, []), ("Z", 1, ["X", "Y"])]
+        cost, path = schedule_tasks(tasks)
+        assert cost == 5
+        assert path[0] in ("X", "Y") and path[-1] == "Z"
+
+    def test_linear_chain(self):
+        """Test simple linear dependency chain."""
+        tasks = [("A", 2, []), ("B", 3, ["A"]), ("C", 4, ["B"])]
+        assert schedule_tasks(tasks) == (9, ["A", "B", "C"])
+
+
+class TestEdgeCases:
+    """Test edge cases and boundary conditions."""
+
+    def test_single_task(self):
+        """Test with a single task and no dependencies."""
+        tasks = [("solo", 5, [])]
+        assert schedule_tasks(tasks) == (5, ["solo"])
+
+    def test_all_independent(self):
+        """Test all tasks run in parallel with no dependencies."""
+        tasks = [("A", 3, []), ("B", 7, []), ("C", 5, [])]
+        cost, path = schedule_tasks(tasks)
+        assert cost == 7
+        assert path == ["B"]
+
+    def test_diamond_dependency(self):
+        """Test diamond-shaped dependency graph."""
+        tasks = [("A", 1, []), ("B", 5, ["A"]), ("C", 2, ["A"]), ("D", 1, ["B", "C"])]
+        assert schedule_tasks(tasks) == (7, ["A", "B", "D"])
+
+    def test_three_node_cycle(self):
+        """Test cycle involving three nodes."""
+        tasks = [("A", 1, ["C"]), ("B", 1, ["A"]), ("C", 1, ["B"])]
+        assert schedule_tasks(tasks) == (-1, [])
+
+    def test_wide_fan_in(self):
+        """Test many tasks feeding into one final task."""
+        tasks = [("A", 1, []), ("B", 2, []), ("C", 3, []), ("D", 4, []), ("final", 1, ["A", "B", "C", "D"])]
+        assert schedule_tasks(tasks) == (5, ["D", "final"])
+
+    def test_deep_chain_with_parallel_branch(self):
+        """Test long chain alongside a shorter parallel branch."""
+        tasks = [
+            ("A", 1, []), ("B", 1, ["A"]), ("C", 1, ["B"]), ("D", 1, ["C"]),
+            ("shortcut", 2, []),
+            ("end", 1, ["D", "shortcut"]),
+        ]
+        assert schedule_tasks(tasks) == (5, ["A", "B", "C", "D", "end"])
+
+    def test_partial_cycle_with_valid_tasks(self):
+        """Test graph where some tasks form a cycle but others don't."""
+        tasks = [("A", 1, []), ("B", 2, ["C"]), ("C", 3, ["B"])]
+        assert schedule_tasks(tasks) == (-1, [])
+
+    def test_large_durations(self):
+        """Test with large task durations."""
+        tasks = [("A", 1000000, []), ("B", 1000000, ["A"])]
+        assert schedule_tasks(tasks) == (2000000, ["A", "B"])