_1290.java

package com.fishercoder.solutions;

import com.fishercoder.common.classes.ListNode;

/**
 * 1290. 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.
 * */
public class _1290 {
    public static class Solution1 {
        public int getDecimalValue(ListNode head) {
            StringBuilder sb = new StringBuilder();
            while (head != null) {
                sb.append(head.val);
                head = head.next;
            }
            return Integer.parseInt(sb.toString(), 2);
        }
    }
}