android-notes/blogs/Algorithm/剑指 Offer/栈相关.md

栈相关

09. 用两个栈实现队列

class CQueue {

    Stack<Integer> putStack, takeStack;

    public CQueue() {
        putStack = new Stack<>();
        takeStack = new Stack<>();
    }

    public void appendTail(int value) {
        putStack.push(value);
    }

    public int deleteHead() {
        if (takeStack.isEmpty()) {
            while (!putStack.isEmpty()) {
                takeStack.push(putStack.pop());
            }
        }
        if (takeStack.isEmpty()) {
            return -1;
        } else {
            return takeStack.pop();
        }
    }
}

30. 包含min函数的栈

class MinStack {

    private Node head;

    public MinStack() {
    }

    public void push(int x) {
        if (head == null) {
            head = new Node(x, x, null);
        } else {
            Node next = head;
            head = new Node(x, Math.min(x, next.min), next);
        }
    }

    public void pop() {
        head = head.next;
    }

    public int top() {
        return head.val;
    }

    public int min() {
        return head.min;
    }

    class Node {
        public int val;
        public int min;
        public Node next;

        public Node(int val, int min, Node next) {
            this.val = val;
            this.min = min;
            this.next = next;
        }
    }
}