1.cpp

/*

Convert Binary Number in a Linked List to Integer
-------------------------------------------------

Given head which is a reference node to a singly-linked list. The value of each node in the linked list is either 0 or 1. The linked list holds the binary representation of a number.

Return the decimal value of the number in the linked list.

 

Example 1:


Input: head = [1,0,1]
Output: 5
Explanation: (101) in base 2 = (5) in base 10
Example 2:

Input: head = [0]
Output: 0
Example 3:

Input: head = [1]
Output: 1
Example 4:

Input: head = [1,0,0,1,0,0,1,1,1,0,0,0,0,0,0]
Output: 18880
Example 5:

Input: head = [0,0]
Output: 0
 

Constraints:

The Linked List is not empty.
Number of nodes will not exceed 30.
Each node's value is either 0 or 1.

*/

class Solution {
public:
    int getDecimalValue(ListNode* head) {
        int ans = head->val;
        while(head->next) {
            ans = (ans << 1) | head->next->val;
            head = head->next;
        }
        return ans;
    }
};