Sword finger offer 30. stack containing min function

Title Description ：

Knowledge point ： Create a stack ,pop(),push(),peek(),Integer_MAX_VALUE

1. Create a stack ,pop(),push(),peek()

Reference resources ： The finger of the sword Offer 09. Queues are implemented with two stacks _jcxj2934 The blog of -CSDN Blog

2.Interger_MAX_VALUE

When comparing the minimum and maximum values , Consider using Integer.MIN_VALUE and Integer.MAX_VALUE

Integer.MAX_VALUE  Express int Can represent the maximum value of an integer 
Integer.MIN_VALUE  Represents the minimum value 

 Use :
min1=Integer.Max_VALUE;
min1 = Math.min(min,x);


max1=Integer.MIN_VALUE;
max1 = Math.max(max1,x);

3. Code

class MinStack {
    private Stack<Integer> st1;
    private Stack<Integer> st2;
    /** initialize your data structure here. */
    public MinStack() {
        // Two stacks 
        st1=new Stack<>();
        st2=new Stack<>(); 
        st2.push(Integer.MAX_VALUE);
    }
    public void push(int x) {
        st1.push(x);
       // min1=Math.min(min1,x);
       // The minimum value should be equal to st2 Top comparison of 
       st2.push(Math.min(st2.peek(),x));
        
    }
    
    public void pop() {
        st1.pop();
        st2.pop();
    }
    
    public int top() {
        return st1.peek();
    }
    
    public int min() {
        
        return st2.peek();
    }
}

/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack obj = new MinStack();
 * obj.push(x);
 * obj.pop(); Just get to the top of the stack , Take a look at , Do not remove 
 * int param_3 = obj.top();
 * int param_4 = obj.min();
 */
 /**
  Ideas ： Go through it , Find the subscript of the minimum 
  Import all the elements on the subscript into the stack 2
 pop()
  Stack 2 Put the element of back on the stack 1
 min Only return without removing 
  */