LeetCode Top-100 T155- minimum stack

A support designed to push, pop, top operation, the stack can be retrieved and smallest elements in constant time.

    push (x) - the element x push the stack.
    pop () - delete elements of the stack.
    top () - get the top element.
    getMin () - retrieve the minimum element in the stack.
Example:

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.

Problem-solving ideas:

Recorded by a stack of min_stack minimum value so that the last getMin () is always the smallest of the stack

Code:

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