Design a max stack that supports push, pop, top, peekMax and popMax.
push(x)
-- Push element x onto stack.pop()
-- Remove the element on top of the stack and return it.top()
-- Get the element on the top.peekMax()
-- Retrieve the maximum element in the stack.popMax()
-- Retrieve the maximum element in the stack, and remove it. If you find more than one maximum elements, only remove the top-most one.
Example 1:
MaxStack stack = new MaxStack(); stack.push(5); stack.push(1); stack.push(5); stack.top(); -> 5 stack.popMax(); -> 5 stack.top(); -> 1 stack.peekMax(); -> 5 stack.pop(); -> 1 stack.top(); -> 5
Note:
- -1e^7 <= x <= 1e^7$
- Number of operations won't exceed 10000.
- The last four operations won't be called when stack is empty.
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