```
class MinStack(object):
def __init__(self):
"""
initialize your data structure here.
"""
# store mins along with data, it takes some extra space, but provides O(1) access to the minimum element
self.mins = []
self.data = []
def push(self, x):
"""
:type x: int
:rtype: void
"""
# if we add the first element it is the minimum
if len(self.data)==0:
self.mins.append(x)
# if not, check whether the element being added is smaller than the current minimum element, if yes it is a new minimum element
else:
if x<self.mins[-1]:
self.mins.append(x)
else:
self.mins.append(self.mins[-1]) # if not the previous element is still the minimum
self.data.append(x)
def pop(self):
"""
:rtype: void
"""
self.mins.pop(-1) # drop the last minimum
return self.data.pop(-1)
def top(self):
"""
:rtype: int
"""
return self.data[-1]
def getMin(self):
"""
:rtype: int
"""
return self.mins[-1]
```