Medium

Quiz

#155 Min Stack

APPROACH

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 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.

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],[],[],[],[]]

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

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What is the optimal approach for this problem?