import java.util.Stack;

public class MinStack_155 {

/**

* 使用辅助栈法

*/

private Stack<Integer> stack;

private Stack<Integer> stackMin;

public MinStack_155() {

stack = new Stack<Integer>();

stackMin = new Stack<Integer>();

}

public void push(int x) {

stack.push(x);

if(stackMin.isEmpty() || x <= stackMin.peek()) {

stackMin.push(x);

}

}

public void pop() {

//注意点：两个Integer对象不能直接用==来判断值是否相等

if(stack.peek().equals(stackMin.peek())) {

stackMin.pop();

}

stack.pop();

}

public int top() {

return stack.peek();

}

public int getMin() {

return stackMin.peek();

}

}