左神算法笔记-实现最小栈

leetcode.cn/problems/mi…

class MinStack {
    // 数据栈
    Stack<Integer> stack;
    // 最小栈：存放最小的数值
    Stack<Integer> minStack;

    public MinStack() {
        stack = new Stack<>();
        minStack = new Stack<>();
    }

    public void push(int val) {
        stack.push(val);
        if(minStack.empty() || val <= minStack.peek()){
            minStack.push(val);
        }else {
            // !min.isEmpty() && val > min.peek()
            minStack.push(minStack.peek());
        }
    }

    public void pop() {
        stack.pop();
        minStack.pop();
    }

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

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