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

function removeDups(node) {
  if(node === null) return null;

  let nodes = new Map();
  let current = node.next;
  let prev = node;
  nodes.set(node.value, 1);

  while(current !== null) {
    if(nodes.get(current.value) === 1) {
      prev.next = current.next;
    } else {
      nodes.set(current.value, 1);
      prev = current;
    }
    current = current.next;
  }
  return node;
}

function removeDups(node) {
    while(node !== null) {
      let current = node;
      while(current.next !== null) {
        if(current.next.value === node.value) {
          current.next = current.next.next;
        } else {
          current = current.next;
        }
      }
      node = node.next;
    }
}

function print(node) {
  while(node !== null) {
      console.log('->' + node.value);
      node = node.next;
  }
}


let node1 = new Node(1);
let node2 = new Node(2);
let node3 = new Node(3);
let node4 = new Node(2);
let node5 = new Node(1);



node1.next = node2;
node2.next = node3;
node3.next = node4;
node4.next = node5;
node5.next = null;

print(removeDups(node1));