Add leetcode 155 task solution

leetcode/stacks/0155_min_stack.py

@@ -0,0 +1,51 @@
+# Link: https://leetcode.com/problems/min-stack/
+from typing import List
+import pytest
+
+
+class MinStack:
+    def __init__(self):
+        self._s: List[int] = []
+        self._min: List[int] = []
+
+    def push(self, val: int) -> None:
+        if len(self._s) == 0:
+            self._min.append(0)
+        elif val < self._s[self._min[-1]]:
+            self._min.append(len(self._s))
+        self._s.append(val)
+
+    def pop(self) -> None:
+        if len(self._s) - 1 == self._min[-1]:
+            self._min.pop()
+        self._s.pop()
+
+    def top(self) -> int:
+        return self._s[-1]
+
+    def getMin(self) -> int:
+        return self._s[self._min[-1]]
+
+
+class TestSuite:
+    @pytest.fixture(autouse=True)
+    def init_tests(self):
+        self.sol = MinStack()
+
+    def test_solution_1(self):
+        self.sol.push(1)
+        self.sol.push(-1)
+        self.sol.push(2)
+        self.sol.push(-2)
+        self.sol.pop()
+        assert self.sol.getMin() == -1
+
+    def test_solution_2(self):
+        breakpoint()
+        self.sol.push(-2)
+        self.sol.push(0)
+        self.sol.push(-1)
+        assert self.sol.getMin() == -2
+        assert self.sol.top() == -1
+        self.sol.pop()
+        assert self.sol.getMin() == -2