Stack.java

package dataStructures.stack;

import dataStructures.singlyLinkedList.SinglyLinkedListNode;

public class Stack {
 
	public SinglyLinkedListNode stack = new SinglyLinkedListNode();

 /**
 * Initialize structure
 */
 public Stack() {

 stack = null;
 }

 /**
 * push new value to the stack
	 * 
 * @param val
	 * @complexity time O(1)
	 * @complexity space O(1)
 */
 public void push(int data) {

 SinglyLinkedListNode a = new SinglyLinkedListNode();
 a.data = data;
 a.next = stack;
 stack = a;
 }
 
 /**
 * pop - remove last value on the stacks peak
	 * 
	 * @complexity time O(1)
	 * @complexity space O(1)
 */
 public void pop() {

 this.stack = this.stack.next;
 }
 
 /**
	 * peek - return last value on the stacks peak
	 * 
 * @return peek
	 * @complexity time O(1)
	 * @complexity space O(1)
 */
 public int peek() {

 int peek = this.stack.data;
 return peek; 
 }

 /**
	 * getMin - return min value in the stack
	 * 
 * @return min value in the stack
	 * @complexity time O(n)
	 * @complexity space O(1)
 */
 public int getMin() {

 SinglyLinkedListNode a = new SinglyLinkedListNode();
 a = this.stack;
 int min = a.data;

 while(a != null) {
 min = (min > a.data)? a.data : min; 
 a = a.next;
 }
 return min; 
 }
}