1290. Convert Binary Number in a Linked List to Integer

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    int getCount(ListNode*&head){
        ListNode *temp = head;
        int cnt = 0;
        while(temp != NULL){
            cnt++;
            temp = temp -> next;
        }
        return cnt;
    }
    int getDecimalValue(ListNode* head) {
        int size = getCount(head);

        int ans = 0;
        ListNode *temp = head;

        while(temp != NULL){
            ans +=( pow(2, size-1) * temp -> val);
            temp = temp -> next;
            size--;
        }

        return ans;
    }
};