Convert Binary Number in a Linked List to Integer

用一个list表示二进制的数, 返回它的十进制表示.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public int getDecimalValue(ListNode head) {
        StringBuilder sb = new StringBuilder();
        while(head != null) {
            sb.append(head.val);
            head = head.next;
        }
        return Integer.parseInt(sb.toString(), 2);
    }
}