# 最小栈
设计一个支持 push ，pop ，top 操作，并能在常数时间内检索到最小元素的栈。
push(x) —— 将元素 x 推入栈中。pop() —— 删除栈顶的元素。top() —— 获取栈顶元素。getMin() —— 检索栈中的最小元素。
示例:
输入：
["MinStack","push","push","push","getMin","pop","top","getMin"]
[[],[-2],[0],[-3],[],[],[],[]]
输出：
[null,null,null,null,-3,null,0,-2]
解释：
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin(); --> 返回 -3.
minStack.pop();
minStack.top(); --> 返回 0.
minStack.getMin(); --> 返回 -2.
提示：
pop、top 和 getMin 操作总是在 非空栈 上调用。
## template
```java
class MinStack {
Stack data_stack;
Stack min_stack;
/** initialize your data structure here. */
public MinStack() {
data_stack = new Stack();
min_stack = new Stack();
}
public void push(int x) {
data_stack.push(x);
if (min_stack.isEmpty()) {
min_stack.push(x);
} else {
if (x > min_stack.peek()) {
x = min_stack.peek();
}
min_stack.push(x);
}
}
public void pop() {
data_stack.pop();
min_stack.pop();
}
public int top() {
return data_stack.peek();
}
public int getMin() {
return min_stack.peek();
}
}
/**
* Your MinStack object will be instantiated and called as such:
* MinStack obj = new MinStack();
* obj.push(x);
* obj.pop();
* int param_3 = obj.top();
* int param_4 = obj.getMin();
*/
```
## 答案
```java
```
## 选项
### A
```java
```
### B
```java
```
### C
```java
```