203. Remove Linked List Elements

Problem

Tags: Linked List, Recursion

Given the head of a linked list and an integer val, remove all the nodes of the linked list that has Node.val == val, and return the new head.

Example 1:

Input: head = [1,2,6,3,4,5,6], val = 6
Output: [1,2,3,4,5]

Example 2:

Input: head = [], val = 1
Output: []

Example 3:

Input: head = [7,7,7,7], val = 7
Output: []

Constraints:

• The number of nodes in the list is in the range [0, 10^4].
• 1 <= Node.val <= 50
• 0 <= val <= 50

Code

JS

// 203. Remove Linked List Elements (11/24/53727)
// Runtime: 126 ms (17.28%) Memory: 43.35 MB (93.75%) 

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} val
 * @return {ListNode}
 */
function removeElements(head, val) {
    let hair = new ListNode(undefined, head);
    let node = hair;
    
    while(node.next) {
        if(node.next.val === val) {
            if(node.next.next) node.next = node.next.next;
            else node.next = null;
        } else node = node.next;
    }
    
    return hair.next;
};