Package g0101_0200.s0155_min_stack

Class MinStack

java.lang.Object

g0101_0200.s0155_min_stack.MinStack

public class MinStack
extends Object

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:

• -231 <= val <= 231 - 1
• Methods pop, top and getMin operations will always be called on non-empty stacks.
• At most 3 * 104 calls will be made to push, pop, top, and getMin.

Constructor Summary

Constructors

Constructor	Description
MinStack()

Method Summary

Modifier and Type	Method	Description
int	getMin()
void	pop()
void	push(int val)
int	top()

Methods inherited from class java.lang.Object

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

Constructor Details

MinStack

public MinStack()

Method Details

push

public void push(int val)

pop

public void pop()

top

public int top()

getMin

public int getMin()