1290. Convert Binary Number in A Linked List to Integer #

题目 #

给定单链表头节点head，已知此链表是一个整数数字的二进制表示形式，链表中每个节点的值非0即1。返回链表所表示数字的十进制值。

思路 #

代码 #

public class ListNode {
    int val;
    ListNode next;
    ListNode() {}
    ListNode(int val) { this.val = val; }
    ListNode(int val, ListNode next) { this.val = val; this.next = next; }
}
class Solution {
    public ListNode reverseList(ListNode head) {
        ListNode prev = null, cur = head, next = head.next;
        while(cur != null) {
            cur.next = prev;
            prev = cur;
            cur = next;
            if (next != null) next = next.next;
        }
        return prev;
    }
    public int getDecimalValue(ListNode head) {
        ListNode newHead = reverseList(head);
        int decimal = 0, digit = 0;
        ListNode ptr = newHead;
        while (ptr != null) {
            decimal += Math.pow(2, digit) * ptr.val;
            digit += 1;
            ptr = ptr.next;
        }
        reverseList(newHead);
        return decimal;
    }
}