Question

我想使用add ()方法按索引插入节点，但它无法帮助修复它。

这就是通话的样子：

list.add ('2', 1); // At the list: '1', '2', '3'

但是当我拨打电话时会触发错误：

throw new Error("Position Node Doesnt Exist!")

我的所有代码：

＆＃13;

class Node {
    constructor(value) {
        this.value = value; // value in the node
        this.next = null; // link to the next node
    }
}

class SinglyLinkedList {
    constructor() {
        /*pointer to the knot-head
         (first element) of the list*/
        this.head = null;
        /*pointer to the node-tail
         (last item) of the list*/
        this.tail = null;
        this.length = 0;
    }

//insert to the beginning (returns the inserted value)
    addFirst(value) {
        //create a new Node
        let newNode = new Node(value);
        //Handle case for when linked list is not empty
        if (this.head) {
            newNode.next = this.head;
            //this.head = newNode;
        } else {//Linked list is empty
            this.tail = newNode;
            //this.head = newNode
        }
        //set the head to the new node
        this.head = newNode;
        //increment count
        this.length++;
    }

//insert to the end(returns the inserted value)
    addLast(value) {
        //create a new Node
        let newNode = new Node(value);
        //Handle case for when linked list is not empty
        if (this.tail) {
            this.tail.next = newNode;
            //this.tail = newNode;
        } else {
            this.head = newNode;
            //this.tail = newNode
        }
        this.tail = newNode;
        //increment count
        this.length++;
    }

    findIndex(item) {
        let currentNode = this.head;
        while (currentNode) {
            if (currentNode.value === item) {
                return currentNode;
            }
            currentNode = currentNode.next;
        }
        return null;
    }

    add(value, index) {
        //create the new node based on the name passed
        let newNode = new Node(value);
        //find the position or item node we want to insert after.
        let positionNode = this.findIndex(index);
        if (positionNode != null) {
            //first set the next pointer of new node to be that of position nodes next
            newNode.next = positionNode.next;
            //finally update the positionNode's next to be the new node
            positionNode.next = newNode;
            this.length++;

        } else {
            //position not found, return error
            throw new Error("Position Node Doesnt Exist!")
        }
    }
}
let list = new SinglyLinkedList();
list.addFirst('1');
list.addLast('3');
list.add('2', 1);
console.log(list);

＆＃13;

Answer 1

您正尝试将字符串与findIndex方法中的数字进行比较：

if (currentNode.value === item) {

要允许自动类型强制，您可以使用双等运算符。或者您可以将两个值转换为相同的类型（数字或字符串）

if (currentNode.value == item) {

请在下面找到已修改的工作代码段。

class Node {
    constructor(value) {
        this.value = value; // value in the node
        this.next = null; // link to the next node
    }
}

class SinglyLinkedList {
    constructor() {
        /*pointer to the knot-head
         (first element) of the list*/
        this.head = null;
        /*pointer to the node-tail
         (last item) of the list*/
        this.tail = null;
        this.length = 0;
    }

//insert to the beginning (returns the inserted value)
    addFirst(value) {
        //create a new Node
        let newNode = new Node(value);
        //Handle case for when linked list is not empty
        if (this.head) {
            newNode.next = this.head;
            //this.head = newNode;
        } else {//Linked list is empty
            this.tail = newNode;
            //this.head = newNode
        }
        //set the head to the new node
        this.head = newNode;
        //increment count
        this.length++;
    }

//insert to the end(returns the inserted value)
    addLast(value) {
        //create a new Node
        let newNode = new Node(value);
        //Handle case for when linked list is not empty
        if (this.tail) {
            this.tail.next = newNode;
            //this.tail = newNode;
        } else {
            this.head = newNode;
            //this.tail = newNode
        }
        this.tail = newNode;
        //increment count
        this.length++;
    }

    findIndex(item) {
        let currentNode = this.head;
        while (currentNode) {
            if (currentNode.value == item) {
                return currentNode;
            }
            currentNode = currentNode.next;
        }
        return null;
    }

    add(value, index) {
        //create the new node based on the name passed
        let newNode = new Node(value);
        //find the position or item node we want to insert after.
        debugger;
        let positionNode = this.findIndex(index);
        if (positionNode != null) {
            //first set the next pointer of new node to be that of position nodes next
            newNode.next = positionNode.next;
            //finally update the positionNode's next to be the new node
            positionNode.next = newNode;
            this.length++;

        } else {
            //position not found, return error
            throw new Error("Position Node Doesnt Exist!")
        }
    }
}
let list = new SinglyLinkedList();
list.addFirst('1');
list.addLast('3');
list.add('2', 1);
console.log(list);

Answer 2

您可以在findIndex内跟踪您所在的索引，而不是比较值。

class Node {
    constructor(value) {
        this.value = value; // value in the node
        this.next = null; // link to the next node
    }
}

class SinglyLinkedList {
    constructor() {
        /*pointer to the knot-head
         (first element) of the list*/
        this.head = null;
        /*pointer to the node-tail
         (last item) of the list*/
        this.tail = null;
        this.length = 0;
    }

//insert to the beginning (returns the inserted value)
    addFirst(value) {
        //create a new Node
        let newNode = new Node(value);
        //Handle case for when linked list is not empty
        if (this.head) {
            newNode.next = this.head;
            //this.head = newNode;
        } else {//Linked list is empty
            this.tail = newNode;
            //this.head = newNode
        }
        //set the head to the new node
        this.head = newNode;
        //increment count
        this.length++;
    }

//insert to the end(returns the inserted value)
    addLast(value) {
        //create a new Node
        let newNode = new Node(value);
        //Handle case for when linked list is not empty
        if (this.tail) {
            this.tail.next = newNode;
            //this.tail = newNode;
        } else {
            this.head = newNode;
            //this.tail = newNode
        }
        this.tail = newNode;
        //increment count
        this.length++;
    }

    findIndex(item) {
        let currentNode = this.head;
        let index = 0;
        while (currentNode) {
            if (index === item - 1) {
                return currentNode;
            }
            index++;
            currentNode = currentNode.next;
        }
        return null;
    }

    add(value, index) {
        //create the new node based on the name passed
        let newNode = new Node(value);
        //find the position or item node we want to insert after.
        let positionNode = this.findIndex(index);
        if (positionNode != null) {
            //first set the next pointer of new node to be that of position nodes next
            newNode.next = positionNode.next;
            //finally update the positionNode's next to be the new node
            positionNode.next = newNode;
            this.length++;

        } else {
            //position not found, return error
            throw new Error("Position Node Doesnt Exist!")
        }
    }
}
let list = new SinglyLinkedList();
list.addFirst('1');
list.addLast('3');
list.add('2', 1);
console.log(list);

Answer 3

您的逻辑似乎有误。 findindex函数查找具有某个值的项。你用索引作为参数调用它......这是错误的。您需要一个index为参数的findItem方法

    if(index<0||index>length) {return null or head or tail...} 
    let currentNode = this.head;
    let currentIndex=0;
    while (currentIndex<index) {
        currentNode = currentNode.next;
        CurrentIndex++;
    }
    return currentNode;

为什么按索引插入节点的方法不起作用？

3 个答案: