Convert Binary Number in a Linked List to Integer

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Unit 6 Session 2 (Click for link to problem statements)

Problem Highlights

• 💡 Difficulty: Easy
• ⏰ Time to complete: 10 mins
• 🛠️ Topics: Linked Lists, Binary Representation

1: U-nderstand

Understand what the interviewer is asking for by using test cases and questions about the problem.

• Established a set (2-3) of test cases to verify their own solution later.
• Established a set (1-2) of edge cases to verify their solution handles complexities.
• Have fully understood the problem and have no clarifying questions.
• Have you verified any Time/Space Constraints for this problem?

• Q: What if the linked list is empty?
  • A: Return 0 as there are no binary digits to convert.

HAPPY CASE
Input: 1 -> 0 -> 1 -> 1
Output: 11
Explanation: The linked list represents the binary number 1011, which equals 11 in decimal.

EDGE CASE
Input: 0
Output: 0
Explanation: The linked list represents the binary number 0, which equals 0 in decimal.

2: M-atch

Match what this problem looks like to known categories of problems, e.g. Linked List or Dynamic Programming, and strategies or patterns in those categories.

This is a typical problem involving the conversion of a binary number stored in a linked list to its decimal equivalent.

3: P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Traverse the linked list while building the binary number and convert it to its decimal form.

1) Initialize a variable to keep track of the number.
2) Traverse the linked list from the head.
3) For each node, multiply the current number by 2 (left shift in binary) and add the node's value.
4) Return the final number.

⚠️ Common Mistakes

• Not considering an empty list, which should return 0.

4: I-mplement

Implement the code to solve the algorithm.

def binary_to_int(head):
    num = 0
    current = head
    while current:
        # Multiply the current number by 2 
        # and add the current node's value to it
        num = num * 2 + current.value
        current = current.next
    return num

5: R-eview

Review the code by running specific example(s) and recording values (watchlist) of your code's variables along the way.

• Use the happy case to check for correct binary to decimal conversion.
• Use the edge case of a single node with 0 to ensure it returns 0.

6: E-valuate

Evaluate the performance of your algorithm and state any strong/weak or future potential work.

• Time Complexity: O(n) where n is the number of nodes in the linked list, as each node is processed once.
• Space Complexity: O(1) because no additional space is required beyond a variable to accumulate the decimal value.