DesignMinStack.py

'''
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(val) pushes the element val 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.
 

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
'''

class MinStack:

    def __init__(self):
        """
        initialize your data structure here.
        """
        self.stack = []
        self.MinStack = []
        

    def push(self, val: int) -> None:
        self.stack.append(val)
        val = min(val, self.MinStack[-1] if self.MinStack else val)
        self.MinStack.append(val)

    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(val)
# obj.pop()
# param_3 = obj.top()
# param_4 = obj.getMin()

'''
Runtime: 56 ms, faster than 90.26% of Python3 online submissions for Min Stack.
Memory Usage: 18.2 MB, less than 34.17% of Python3 online submissions for Min Stack.
'''