C3P6.java

package chapter3;

import java.util.Stack;

/*
 * Career Cup 3.6
 * 
 * Write a program to sort a stack in ascending order (with biggest items on top).
 * You may use additional stacks to hold items, but you may not copy the elements into any other data structure 
 * (such as an array). The stack supports the following operations: push, pop, peek, and isEmpty.
 */
public class C3P6 {

  Stack<Integer> s1 = new Stack<Integer>();
	Stack<Integer> s2 = new Stack<Integer>();
	
	public C3P6(int array[]){
		for (int i = 0; i < array.length; i++) {
			s1.push(array[i]);
		}
	}
	
	public void sort(){
		while(!s1.isEmpty()){
			int data = s1.pop();
			while(!s2.isEmpty() && s2.peek() < data){
				s1.push(s2.pop());
			}
			s2.push(data);
		}
		while(!s2.isEmpty()) {
			s1.push(s2.pop());
		}
	}
	
	
	public static void main(String[] args) {
		int array[] = {2, 4, 9, 3, 7};
		C3P6 problem = new C3P6(array);
		System.out.println(problem.s1);
		problem.sort();
		System.out.println(problem.s1);
	}

}