how to remove all item from list in javascript

Question

how to remove Remove all elements from a linked list of integers that have value val.

example

Input:  1->2->6->3->4->5->6, val = 6
Output: 1->2->3->4->5

I tried like this

var removeElements = function (head, val) {
        if (!head) return null;

        let curr = head,
            pre = curr;

        while (curr != null) {
            if (curr.val == val) {
                pre.next = curr.next
                curr = curr.next;
            } else {
                pre = curr;
                curr = curr.next;
            }
        }

        return head
    };

my first test case working fine

console.log(JSON.stringify(removeElements(
    {
        "val": 1,
        "next": {
            "val": 2,
            "next": {
                "val": 6,
                "next":
                    {
                        "val": 3,
                        "next":
                            {
                                "val": 4,
                                "next":
                                    {
                                        "val": 5, "next":
                                            {"val": 6, "next": null}
                                    }
                            }
                    }
            }
        }
    }
    , 6)));
// working fine
// expected  1->2->3->4->5 or [1,2,3,4,5]

but it fail below case

console.log(JSON.stringify(removeElements(
    {
        "val": 1,
        "next": {
            "val": 1,
            "next": null
        }
    }, 1)));
// getting {"val":1,"next":null} or [1]
// expected null or []

please suggest how to achieve this.I am storing the current node in previous node

The function doesn't work if the matching element is in head, since you return head all the time. — Barmar
– Barmar, Commented Mar 24, 2020 at 3:22
ok trying like this while (head!=null){ if(head.val == val){ head = head.next; }else { break; } } — user12130378
– user12130378, Commented Mar 24, 2020 at 3:44

user12130378 · Accepted Answer · 2020-03-24 03:46:02Z

1

for special case I check like this

var removeElements = function (head, val) {
    if (!head) return null;

    while (head!=null){
        if(head.val == val){
            head = head.next;
        }else {
            break;
        }
    }

    let curr = head,
        pre = curr;

    while (curr != null) {
        if (curr.val == val) {
            pre.next = curr.next
            curr = curr.next;
        } else {
            pre = curr;
            curr = curr.next;
        }
    }

    return head
};

answered Mar 24, 2020 at 3:46

user12130378

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Comments

edu · Accepted Answer · 2020-03-24 03:59:19Z

0

I apologize if I didn't understand the question, is this what you're looking for?

var removeElements = function (head, val) {
    if (!head) return null;

    let curr = head;
    let pre = null;

    while (curr != null) {
        if (curr.val == val) {
            if (pre) {
                pre.next = curr.next;
            } else {
                head = curr.next;
            }
        } else {
            pre = curr;
        }
        curr = curr.next;
    }

    return head;
};

edited Mar 24, 2020 at 3:59

answered Mar 24, 2020 at 3:54

edu

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