155. Min Stack

Easy

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. push(x) -- Push element x onto stack. pop() -- Removes the element on top of the stack. top() -- Get the top element. getMin() -- Retrieve the minimum element in the stack.

😇 Solution

O(1)

class MinStack:

    def __init__(self):
        self.q = []


    def push(self, x):
        curMin = self.getMin()
        if curMin == None or x < curMin:
            curMin = x
        self.q.append((x, curMin));

        
    def pop(self):
        self.q.pop()

        
    def top(self):
        if len(self.q) == 0:
            return None
        else:
            return self.q[len(self.q) - 1][0]

        
    def getMin(self):
        if len(self.q) == 0:
            return None
        else:
            return self.q[len(self.q) - 1][1]