refactor(work): restructure solution directories with bucket level and add .gitkeep placeholders

work/1/Medium/Stack/155.min-stack.py

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+"""
+155. Min Stack
+Difficulty: Medium
+https://leetcode.com/problems/min-stack/
+
+──────────────────────────────────────────────────
+
+Design a stack that supports push, pop, top, and retrieving the
+minimum element in constant time.
+
+Implement the MinStack class:
+
+        • MinStack() initializes the stack object.
+
+        • void push(int value) pushes the element value onto the stack.
+
+        • void pop() removes the element on the top of the stack.
+
+        • int top() gets the top element of the stack.
+
+        • int getMin() retrieves the minimum element in the stack.
+
+You must implement a solution with O(1) time complexity for each
+function.
+
+
+
+Example 1:
+
+Input
+["MinStack","push","push","push","getMin","pop","top","getMin"]
+[[],[-2],[0],[-3],[],[],[],[]]
+
+Output
+[null,null,null,null,-3,null,0,-2]
+
+Explanation
+MinStack minStack = new MinStack();
+minStack.push(-2);
+minStack.push(0);
+minStack.push(-3);
+minStack.getMin(); // return -3
+minStack.pop();
+minStack.top();    // return 0
+minStack.getMin(); // return -2
+
+
+
+Constraints:
+
+        • -2^31 <= val <= 2^31 - 1
+
+• Methods pop, top and getMin operations will always be called on
+non-empty stacks.
+
+        • At most 3 * 10^4 calls will be made to push, pop, top, and getMin.
+"""
+
+
+class MinStack:
+    def __init__(self):
+        self.stack = []
+        self.minStack = []
+
+    def push(self, value: int) -> None:
+        self.stack.append(value)
+        value = min(value, self.minStack[-1] if self.minStack else value)
+        self.minStack.append(value)
+
+    def pop(self) -> None:
+        self.stack.pop()
+        self.minStack.pop()
+
+    def top(self) -> int:
+        return self.stack[-1]
+
+    def getMin(self) -> int:
+        return self.minStack[-1]
+
+
+# Your MinStack object will be instantiated and called as such:
+# obj = MinStack()
+# obj.push(value)
+# obj.pop()
+# param_3 = obj.top()
+# param_4 = obj.getMin()