Add Two Numbers Represented as Linked List in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does each node in the linked list represent in the problem 'Add Two Numbers Represented as Linked List'?

Each node represents a single digit of a number, stored in reverse order (the 1's digit is at the head).

beginner

Why do we add digits starting from the head of the linked lists in this problem?

Because the digits are stored in reverse order, the head contains the least significant digit, so addition starts from the units place.

beginner

What is the role of the carry in adding two numbers represented as linked lists?

The carry stores the overflow digit when the sum of two digits exceeds 9, and it is added to the next pair of digits.

intermediate

How do you handle linked lists of different lengths when adding two numbers represented as linked lists?

Continue adding digits until both lists are fully traversed, treating missing digits as 0, and include any remaining carry.

intermediate

What is the time complexity of adding two numbers represented as linked lists?

The time complexity is O(max(m, n)) where m and n are the lengths of the two linked lists, since each node is processed once.

In the problem 'Add Two Numbers Represented as Linked List', what does the head node represent?

A The carry digit

B The most significant digit

C The middle digit

D The least significant digit

The head node stores the least significant digit because the number is stored in reverse order.

What should you do if one linked list is longer than the other during addition?

A Continue adding with the longer list's digits and carry

B Reverse the longer list

C Ignore the extra digits

D Stop when the shorter list ends

You continue adding the remaining digits of the longer list along with any carry.

What is the purpose of the carry variable in the addition process?

A To store the sum of digits

B To count the number of nodes

C To store the overflow digit from sum > 9

D To reverse the linked list

Carry holds the overflow digit when the sum of two digits is greater than 9.

If the sum of the last digits plus carry is 15, what digit is stored in the new node?

A 5

B 1

C 0

D 15

Only the last digit (5) is stored; the carry (1) is passed to the next addition.

What is the output linked list for adding (2 -> 4 -> 3) and (5 -> 6 -> 4)?

A 8 -> 0 -> 7

B 7 -> 0 -> 8

C 7 -> 10 -> 7

D 7 -> 6 -> 7

342 + 465 = 807, stored as 7 -> 0 -> 8 in reverse order.

Explain step-by-step how to add two numbers represented as linked lists.

Think about how you add numbers on paper from right to left.

Describe how to handle the carry when adding two linked lists digit by digit.

Carry is like the extra you keep for the next column in addition.