#155

Min Stack

specialist · 750 · lc medium +31 · 57.8% accepted · 15,893 likes · top 54%

Description

Build a stack that also supports constant-time retrieval of the minimum element.

Implement the MinStack class:

- MinStack() initializes the stack object.

- void push(int val) pushes val onto the stack.

- void pop() removes the top element.

- int top() returns the top element.

- int getMin() returns the current minimum element in the stack.

All five operations must run in O(1) time.

Example 1:

Input

["MinStack","push","push","push","getMin","pop","top","getMin"]

[[],[-2],[0],[-3],[],[],[],[]]

Example 2:

Output

[null,null,null,null,-3,null,0,-2]

Example 3:

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

Code

class MinStack:

    def __init__(self):
        

    def push(self, val: int) -> None:
        

    def pop(self) -> None:
        

    def top(self) -> int:
        

    def getMin(self) -> int:
        


# 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()

class MinStack:

    def __init__(self):
        

    def push(self, val: int) -> None:
        

    def pop(self) -> None:
        

    def top(self) -> int:
        

    def getMin(self) -> int:
        


# 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()