Understanding the LeetCode Problem: Mean of Three Big Int Linked List

When tackling the problem “Mean of Three Big Int Linked List” on LeetCode, you’re faced with a unique challenge that requires a deep understanding of linked list manipulation and arithmetic operations on large integers. This article will guide you through the intricacies of the problem, providing a detailed explanation of the approach, the code, and the thought process behind it.

Problem Description

The problem statement is straightforward: you are given three linked lists, each containing big integers. Your task is to compute the mean of these three big integers and return it as a linked list. The challenge lies in handling the large integers and ensuring the mean is calculated correctly.

Approach

1. Traverse each linked list to sum up the integers.2. Calculate the total sum of all three linked lists.3. Divide the total sum by 3 to get the mean.4. Convert the mean to a linked list format and return it.

Step-by-Step Explanation

Let’s break down the approach into smaller, manageable steps.

Step 1: Traverse and Sum

In this step, you need to traverse each linked list and sum up the integers. This requires a loop that iterates through each node of the linked list, adding the node’s value to a running total.

Step 2: Calculate Total Sum

Once you have the sum of each linked list, you add these sums together to get the total sum. This is a straightforward arithmetic operation.

Step 3: Compute Mean

Divide the total sum by 3 to get the mean. Since the integers are big, you need to handle the division carefully to avoid overflow or incorrect results.

Step 4: Convert to Linked List

Finally, you need to convert the mean back into a linked list format. This involves creating a new linked list and inserting the mean value into it.

Code Implementation

Below is a sample code implementation in Python. Note that this is a high-level implementation and does not include error handling or optimizations.

class ListNode:    def __init__(self, val=0, next=None):        self.val = val        self.next = nextdef addTwoNumbers(l1, l2):    dummy = ListNode(0)    current = dummy    carry = 0    while l1 or l2 or carry:        val1 = l1.val if l1 else 0        val2 = l2.val if l2 else 0        sum_val = val1 + val2 + carry        carry = sum_val // 10        current.next = ListNode(sum_val % 10)        current = current.next        if l1:            l1 = l1.next        if l2:            l2 = l2.next    return dummy.nextdef meanOfThreeBigIntLinkedList(l1, l2, l3):    sum1 = sumList(l1)    sum2 = sumList(l2)    sum3 = sumList(l3)    total_sum = sum1 + sum2 + sum3    mean = total_sum // 3    return convertToLinkedList(mean)def sumList(head):    current = head    total = 0    while current:        total += current.val        current = current.next    return totaldef convertToLinkedList(num):    dummy = ListNode(0)    current = dummy    while num > 0:        current.next = ListNode(num % 10)        current = current.next        num //= 10    return dummy.next

Conclusion

Handling big integers in linked lists can be challenging, but with the right approach, you can solve the problem efficiently. The key is to break down the problem into smaller steps and handle each step carefully. By following the approach outlined in this article, you should be able to solve the “Mean of Three Big Int Linked List” problem on LeetCode.