phase 5 part 5: cs algorithms, network-os, web-security topics with tested examples; all 43 stacks pass --strict

topics/cs/algorithms/examples/patterns/test_patterns.py

@@ -0,0 +1,63 @@
+import random
+
+import pytest
+
+from patterns import (LRUCache, edit_distance, longest_unique_substring, lower_bound, merge_intervals,
+                      shortest_path, top_k_frequent, topo_order, two_sum)
+
+
+def test_two_sum():
+    assert two_sum([3, 3], 6) == (0, 1)
+    assert two_sum([1, 2], 10) is None
+
+
+@pytest.mark.parametrize("s,n", [("", 0), ("bbbb", 1), ("pwwkew", 3), ("abba", 2), ("你好你们好", 3)])
+def test_longest_unique(s, n):
+    assert longest_unique_substring(s) == n
+
+
+def test_lower_bound_matches_bisect():
+    import bisect
+    rng = random.Random(0)
+    for _ in range(200):                     # 与标准库对拍
+        arr = sorted(rng.randint(0, 20) for _ in range(rng.randint(0, 15)))
+        t = rng.randint(-1, 21)
+        assert lower_bound(arr, t) == bisect.bisect_left(arr, t)
+
+
+def test_top_k():
+    assert top_k_frequent([], 3) == []
+    assert top_k_frequent(list("aaabbc"), 1) == ["a"]
+
+
+def test_shortest_path_blocked():
+    assert shortest_path([[0, 1], [1, 0]], (0, 0), (1, 1)) == -1
+    assert shortest_path([[0]], (0, 0), (0, 0)) == 0
+
+
+def test_topo_cycle_and_order():
+    assert topo_order({"a": ["b"], "b": ["a"]}) is None
+    order = topo_order({"app": ["db", "cache"], "cache": ["net"], "db": ["net"]})
+    assert order is not None
+    pos = {n: i for i, n in enumerate(order)}
+    assert pos["net"] < pos["db"] < pos["app"] and pos["net"] < pos["cache"] < pos["app"]
+
+
+def test_edit_distance():
+    assert edit_distance("", "abc") == 3
+    assert edit_distance("退货申请", "退款申请") == 1
+
+
+def test_lru():
+    c = LRUCache(2)
+    c.put("a", 1)
+    c.put("b", 2)
+    assert c.get("a") == 1                   # a 变成最近使用
+    c.put("c", 3)                            # 淘汰 b
+    assert c.get("b") is None and c.get("a") == 1 and c.get("c") == 3
+
+
+def test_merge_intervals():
+    assert merge_intervals([]) == []
+    assert merge_intervals([(1, 4), (4, 5)]) == [(1, 5)]
+    assert merge_intervals([(5, 6), (1, 2)]) == [(1, 2), (5, 6)]