Today I have done leetcode's December LeetCoding Challenge with cpp.

December LeetCoding Challenge 7

Description

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.

Solution

class Solution {
public:
  int getDecimalValue(ListNode* head) {
    int ans = 0;
    while(head) {
      ans <<= 1;
      ans |= head->val;
      head = head->next;
    }
    return ans;
  }
};

// Accepted
// 102/102 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 93.93 % of cpp submissions (8.1 MB)