面试算法——4.栈的反转

将已知的栈，利用递归实现反转。

附加字符串的反转，总结反转的递归思路。

package ch_1_stackandqueue;

import java.util.Stack;

public class Pro_3_ReverseStack {
	
	private int getLastElement(Stack<Integer> stack)
	{
		int res=stack.pop();
		if(stack.isEmpty())
		{
			return res;
		}
		else
		{
			int last=getLastElement(stack);
			stack.push(res);
			return last;
		}
	}
	
	public void reverse(Stack<Integer> stack)
	{
		if(stack.isEmpty())
		{
			return;
		}
		else {
			int i = getLastElement(stack);
			reverse(stack);
			stack.push(i);
			System.out.println(i);
		}		
	}

	public String reverse_String(String string)
	{
		if(string.length()<=0)
		{
			return "";
		}else
		{
			return string.charAt(string.length()-1)+reverse_String(string.substring(0,string.length()-1));
		}
	}
	
	static Stack<Integer> stack;
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Pro_3_ReverseStack test = new Pro_3_ReverseStack();
		
		//将顺序反转，一般递归思路是将最后一个特殊处理
		//剩下部分再反转
		//递归终止条件是为空
		//System.out.println(test.reverse_String("123"));;
		stack = new Stack<>();
		stack.push(1);
		stack.push(2);
		stack.push(3);
		stack.push(4);
		
		test.reverse(stack);
		/*while(!stack.isEmpty())
		{
			System.out.println(stack.pop());
		}*/
	}

}