One way linked list implements queue and stack

One way list and two-way list

Single chain list ： value , One next The pointer

Double linked list ： value , One last The pointer , One next The pointer

Single linked list implementation queue

queue ： fifo

You need two variables head and tail

 

public static class Node<V> {
        public V value;
        public Node<V> next;

        public Node(V v) {
            value = v;
            next = null;
        }
}
public static class MyQueue<V> {
        private Node<V> head;
        private Node<V> tail;
        private int size;

        // initialization 
        public MyQueue() {
            head = null;
            tail = null;
            size = 0;
        }

        public boolean isEmpty() {
            return size == 0;
        }

        public void offer(V value) {
            Node<V> cur = new Node<V>(value);
            if (tail == null) {
                head = cur;
                tail = cur;
            } else {
                tail.next = cur;
                tail = cur;
            }
            size++;
        }

        // eject 
        public V poll() {
            V ans = null;
            if (head != null) {
                ans = head.value;
                head = head.next;
                size--;
            }
            if (head == null) {
                tail = null;
            }
            return ans;
        }

        // Take value only   Don't pop up 
        public V peek() {
            V ans = null;
            if (head != null) {
                ans = head.value;
            }
            return ans;
        }
 }

Implementation stack

Stack ： First in, then out

Just one variable , Stack a node ,head Point to a new node ,head = head.next

    /**
     *  Single linked list implementation stack 
     *
     * @param <V>
     */
    public static class MyStack<V> {
        private Node<V> head;
        private int size;

        public MyStack() {
            head = null;
            size = 0;
        }

        public boolean isEmpty() {
            return size == 0;
        }

        public int size() {
            return size;
        }

        public void push(V value) {
            Node<V> cur = new Node<>(value);
            if (head == null) {
                head = cur;
            } else {
                cur.next = head;
                head = cur;
            }
            size++;

        }

        public V pop() {
            V ans = null;
            if (head != null) {
                ans = head.value;
                head = head.next;
                size--;
            }
            return ans;
        }

        public V peek() {
            return head != null ? head.value : null;
        }
    }