leetcode Min Stack

题目：

Design a supports push, pop, top, and retrieving the minimum element in constant time.

• push(x) -- Push element x onto stack.
• pop() -- Removes the element on top of the stack.
• top() -- Get the top element.
• getMin() -- Retrieve the minimum element in the stack.

这道题没有编出来。。。。

class MinStack {
   private Stack<Integer>stack=new Stack<Integer>();
private Stack<Integer>minstack=new Stack<Integer>();


public void push(int x) {
    stack.push(x);
    if(minstack.size()!=0){
        if(x<=minstack.peek()){
            minstack.push(x);
        }
    }else{
        minstack.push(x);
    }
    
}
   

public void pop() {
   int x=stack.pop();
   if(x==minstack.peek()){
       minstack.pop();
   }
}

public int top() {
   return stack.peek();
}

public int getMin() {
   return minstack.peek();
}

}