Package g0101_0200.s0155_min_stack

Class MinStack

  • All Implemented Interfaces:
    
public final class MinStack

    155 - Min Stack.

    Easy

    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.

    Example 1:

    Input

    ["MinStack","push","push","push","getMin","pop","top","getMin"]
[ [],[-2],[0],[-3],[],[],[],[]]

    Output: null,null,null,null,-3,null,0,-2

    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

    Constraints:

    • <code>-2<sup>31</sup><= val <= 2<sup>31</sup> - 1</code>

    • Methods pop, top and getMin operations will always be called on non-empty stacks.

    • At most <code>3 * 10<sup>4</sup></code> calls will be made to push, pop, top, and getMin.

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description

    • Field Summary

      Fields 
      Modifier and Type Field Description

    • Constructor Summary

      Constructors 
      Constructor Description
      MinStack()

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      final Unit push(Integer x)
      final Unit pop()
      final Integer top()
      final Integer getMin()

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait