二进制链表转整数

https://leetcode-cn.com/problems/convert-binary-number-in-a-linked-list-to-integer/

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public int getDecimalValue(ListNode head) {
        int res = 0;
        if(head == null) return res;
        ListNode p = head;
        while(p != null){
            res = res * 2 + p.val;
            p = p.next;
        }
        return res;
    }
}