From a3819c9b265e67ea3a1e27a7d95f91f93586e228 Mon Sep 17 00:00:00 2001
From: Dan Buch <dan@meatballhat.com>
Date: Sat, 21 Oct 2023 07:18:56 -0400
Subject: [PATCH] A poorly-made min stack

---
 leetcode/stuff.py      | 24 +++++++++++++++++++++
 leetcode/test_stuff.py | 49 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/leetcode/stuff.py b/leetcode/stuff.py
index c6682c1..0525b95 100644
--- a/leetcode/stuff.py
+++ b/leetcode/stuff.py
@@ -138,3 +138,27 @@ class Roman:
             total += cls.ALL[c]
 
         return total
+
+
+class MinStack:
+    def __init__(self):
+        self._v: list[int] = []
+        self._min: int | None = None
+
+    def push(self, val: int) -> None:
+        self._v.append(val)
+
+        if self._min is None or self._min > val:
+            self._min = val
+
+    def pop(self) -> None:
+        popped = self._v.pop(-1)
+
+        if popped == self._min:
+            self._min = min(self._v)
+
+    def top(self) -> int:
+        return self._v[-1]
+
+    def getMin(self) -> int:  # no qa
+        return typing.cast(int, self._min)
diff --git a/leetcode/test_stuff.py b/leetcode/test_stuff.py
index 6238589..87418a6 100644
--- a/leetcode/test_stuff.py
+++ b/leetcode/test_stuff.py
@@ -28,3 +28,52 @@ def test_find_sqrt_ish(n: int, expected: int):
 )
 def test_int_to_roman(n: int, expected: str):
     assert stuff.Roman.i2r(n) == expected
+
+
+@pytest.mark.parametrize(
+    ("ops", "expected"),
+    [
+        (
+            (
+                [
+                    ("new",),
+                    ("push", -2),
+                    ("push", 0),
+                    ("push", -3),
+                    ("getMin",),
+                    ("pop",),
+                    ("top",),
+                    ("getMin",),
+                ]
+            ),
+            [
+                None,
+                None,
+                None,
+                None,
+                -3,
+                None,
+                0,
+                -2,
+            ],
+        )
+    ],
+)
+def test_min_stack(ops: list[tuple[str] | tuple[str, int]], expected: list[int | None]):
+    returned: list[int | None] = []
+    inst: stuff.MinStack | None = None
+
+    for op in ops:
+        if len(op) == 1:
+            if op[0] == "new":
+                inst = stuff.MinStack()
+                returned.append(None)
+                continue
+
+            returned.append(getattr(inst, op[0])())
+            continue
+
+        method, arg = op
+        returned.append(getattr(inst, method)(arg))
+
+    assert returned == expected