Stack with min() operation
Problem Statement Create a stack data structure that supports the following operations as efficiently as possible: Push, which adds a new element atop the stack, Pop, which removes the top element of the stack, Find-Min, which returns (but does not remove) the smallest element of the stack Full Code
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package stacksqueues; import java.util.ArrayList; import java.util.LinkedList; import java.util.List; import datastructures.MyStack; /** * How would you design a stack which, in addition to push and pop, also has a function min which returns the minimum * element? Push, pop and min should all operate in O(1) time. * * @author lucas */ public class E2 { protected static class MyStackWithMin extends MyStack { MyStack mins; public MyStackWithMin() { mins = new MyStack<Integer>(); } public void push(int item) { super.push(item); if (item <= min()) { mins.push(item); } } public Integer pop() { int item = (int) super.pop(); if (item == min()) { mins.pop(); } return item; } /** * Return min element on stack * * @return */ public int min() { if (mins.isEmpty()) { return Integer.MAX_VALUE; } else { return (int)mins.peek(); } } } public static void main(String[] args) { MyStackWithMin stack = new MyStackWithMin(); stack.push(3); stack.push(31); stack.push(13); stack.push(2); stack.push(5); System.out.println(stack.min()); } } |