Java中LinkeLlist源码阅读

面试题: 取链表中倒数第k的值:

public void getLinkedListObj(LinkedList linkedList,int k){
    if(linkedList.isEmpty()){
        System.out.print("集合为空...");
        return;
    }
    int size = linkedList.size();
    if(k<=0||k>size){
        System.err.print("输入的k值超出范围...");
        return;
    }
    Object o = linkedList.get(size - k);
    System.out.print(o);
}

    Java中LinkedList存在get(int index)方法 所以比较好操作.

    通过源码看:

    get(int index):

public E get(int index) {
    checkElementIndex(index);
    return node(index).item;
}

1.先检查index 时候超出范围

2.node(index).item方法:

    LinkedList中定义了内部class:

        

private static class Node<E> {
    E item;
    Node<E> next;
    Node<E> prev;

    Node(Node<E> prev, E element, Node<E> next) {
        this.item = element;
        this.next = next;
        this.prev = prev;
    }
}

item就像保存 LinkedList中的元素;

node(index):

Node<E> node(int index) {
    // assert isElementIndex(index);

    if (index < (size >> 1)) {
        Node<E> x = first;
        for (int i = 0; i < index; i++)
            x = x.next;
        return x;
    } else {
        Node<E> x = last;
        for (int i = size - 1; i > index; i--)
            x = x.prev;
        return x;
    }
}

这里采用了2分法 进行遍历取值;