convert-binary-number-in-a-liked-list-to-integer.cpp

//question//


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.



//solution//

/**
 * 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 getDecimalValue(ListNode* head) {
        int value;
        string s ="";
        while(head!=NULL)
        {
            value = head->val;
            s += to_string(value);
            head= head->next;
        }
        int ans=0,power=0;
        for(int i=s.size()-1;i>=0;i--)
        {
            value = s[i]-'0';
            ans += value*pow(2,power);
            power++;
        }
        return ans;
    }
};