import java.util.Stack;
/**
* 设计一个特殊的栈，在实现栈的基本功能的基础上，再实现返回栈中最小元素的操作
* @author 21405
*
*/
public class SpecialStack {
private Stack<Integer> stackData;
private Stack<Integer> stackMin;
public SpecialStack(){
this.stackData =
new Stack<Integer>();
this.stackMin =
new Stack<Integer>();
}
/**
* 入栈
* <p> stackData 用作普通的栈，stackMin用作存最小值的栈
* @throws Exception
*/
public void push(
int A)
throws Exception{
if(stackData.isEmpty() && stackMin.isEmpty()){
stackData.push(A);
stackMin.push(A);
}
else{
if(A < getMin()){
stackMin.push(A);
stackData.push(A);
}
else{
stackData.push(A);
}
}
}
/**
* 出栈
* @throws Exception
*/
public int pop()
throws Exception{
if(stackData.peek() == getMin()){
stackMin.pop();
}
return stackData.pop();
}
/**
* 获取最小值
* @throws Exception
*/
public int getMin()
throws Exception{
if(
this.stackMin.isEmpty()){
throw new Exception(
"Stack is empty");
}
return stackMin.peek();
}
}
