From 421f2e783af773712a5e7a799f7cbaca69ab7a21 Mon Sep 17 00:00:00 2001
From: Haidong Ji
Date: Thu, 21 Feb 2019 21:32:22 -0600
Subject: Priority queue parallel job processing done!

Not too bad since I worked it out in Java. Good practice of heapq module in Python! A lot of fun :)
---
 sources/job_queue.py   | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 tests/job_queueTest.py | 28 ++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+)
 create mode 100644 sources/job_queue.py
 create mode 100644 tests/job_queueTest.py

diff --git a/sources/job_queue.py b/sources/job_queue.py
new file mode 100644
index 0000000..8928d4a
--- /dev/null
+++ b/sources/job_queue.py
@@ -0,0 +1,47 @@
+# python3
+
+from heapq import heappush, heappop
+from collections import namedtuple
+
+AssignedJob = namedtuple("AssignedJob", ["worker", "started_at"])
+
+
+def assign_jobs(n_workers, jobs):
+    # Naive algorithm
+    result = []
+    next_free_time = [0] * n_workers
+    for job in jobs:
+        next_worker = min(range(n_workers), key=lambda w: next_free_time[w])
+        result.append(AssignedJob(next_worker, next_free_time[next_worker]))
+        next_free_time[next_worker] += job
+
+    return result
+
+
+def assign_jobs_improved(n_workers, jobs):
+    result = []
+    worker_priority_q = []
+    for i in range(n_workers):
+        heappush(worker_priority_q, (0, i))
+
+    for j in range(len(jobs)):
+        pair = heappop(worker_priority_q)
+        result.append(AssignedJob(pair[1], pair[0]))
+        heappush(worker_priority_q, (pair[0] + jobs[j], pair[1]))
+
+    return result
+
+
+def main():
+    n_workers, n_jobs = map(int, input().split())
+    jobs = list(map(int, input().split()))
+    assert len(jobs) == n_jobs
+
+    assigned_jobs = assign_jobs_improved(n_workers, jobs)
+
+    for job in assigned_jobs:
+        print(job.worker, job.started_at)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/tests/job_queueTest.py b/tests/job_queueTest.py
new file mode 100644
index 0000000..ac95c35
--- /dev/null
+++ b/tests/job_queueTest.py
@@ -0,0 +1,28 @@
+import unittest
+
+from collections import namedtuple
+
+AssignedJob = namedtuple("AssignedJob", ["worker", "started_at"])
+
+from sources.job_queue import assign_jobs, assign_jobs_improved
+
+
+class MyTestCase(unittest.TestCase):
+    def test(self):
+        num_workers = 2
+        jobs = [1, 2, 3, 4, 5]
+        result = [AssignedJob(0, 0), AssignedJob(1, 0), AssignedJob(0, 1), AssignedJob(1, 2), AssignedJob(0, 4)]
+        self.assertListEqual(result, assign_jobs_improved(num_workers, jobs))
+
+    def test1(self):
+        num_workers = 4
+        jobs = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
+        result = [AssignedJob(0, 0), AssignedJob(1, 0), AssignedJob(2, 0), AssignedJob(3, 0), AssignedJob(0, 1),
+                  AssignedJob(1, 1), AssignedJob(2, 1), AssignedJob(3, 1), AssignedJob(0, 2), AssignedJob(1, 2),
+                  AssignedJob(2, 2), AssignedJob(3, 2), AssignedJob(0, 3), AssignedJob(1, 3), AssignedJob(2, 3),
+                  AssignedJob(3, 3), AssignedJob(0, 4), AssignedJob(1, 4), AssignedJob(2, 4), AssignedJob(3, 4)]
+        self.assertListEqual(result, assign_jobs_improved(num_workers, jobs))
+
+
+if __name__ == '__main__':
+    unittest.main()
-- 
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