155. Min Stack

 

 

不是min就直接push一个min刀minStack

 

class MinStack {

    /** initialize your data structure here. */
    Stack<Integer> stack, min;
    public MinStack() {
        stack = new Stack<>();
        min = new Stack<>();    
    }
    
    public void push(int x) {
        stack.push(x);
        if(min.isEmpty() || x <= min.peek()){
            min.push(x);
        }else{
            min.push(min.peek());
        }
        
    }
    
    public void pop() {
        stack.pop();
        min.pop();
        
    }
    
    public int top() {
        return stack.peek();
        
    }
    
    public int getMin() {
        return min.peek();
    }
}