w-linkedList-SumList.js

// https://structy.net/problems/sum-list

//

class Node {
  constructor(val) {
    this.val = val;
    this.next = null;
  }
}

// const sumList = (head) => {
//   //
//   let count = 0;
//   while (head) {
//     count += head.val;
//     head = head.next;
//   }
//   console.log(count);
//   return count;
// };

const sumList = (head) => {
  if (!head) return 0;
  return head.val + sumList(head.next);
};

const a = new Node(2);
const b = new Node(8);
const c = new Node(3);
const d = new Node(-1);
const e = new Node(7);

a.next = b;
b.next = c;
c.next = d;
d.next = e;

// 2 -> 8 -> 3 -> -1 -> 7

sumList(a); // 19