C++

1class Solution {
2  public:
3    int getDecimalValue(ListNode* head) {
4      unsigned long result = 0;
5
6      while (true)
7      {
8        result = result  << 1 + head->val;
9        head = head->next;
10
11        if (head == NULL || head == nullptr) break;
12      }
13
14      return result;
15    }
16};

JavaScript

1var getDecimalValue = function(head) {
2  let result = 0;
3
4  while (true) {
5    result = result * 2 + head.val;
6    if (head.next === null) break;
7    head = head.next;
8  }
9
10  return result;
11};

Ruby

1def get_decimal_value(head)
2  result = 0
3
4  while true do
5    result = result * 2 + head.val
6    head = head.next
7
8    break if head == nil
9  end
10
11  result
12end