Add to Array-Form of Integer

Add to Array-Form of Integer is a Easy Data Structures and Algorithms interview problem you can solve, run and submit on Thita.ai. It belongs to the Array/Matrix Manipulation Patterns pattern, in the Plus One (Handling Carry) subpattern.

Problem statement

The array-form of an integer num is an array representing its digits in left to right order.

For example, for num = 1321, the array form is [1,3,2,1].

Given num, the array-form of an integer, and an integer k, return the array-form of the integer num + k.

Example 1: Input: num = [1,2,0,0], k = 34 Output: [1,2,3,4] Explanation: 1200 + 34 = 1234

Example 2: Input: num = [2,7,4], k = 181 Output: [4,5,5] Explanation: 274 + 181 = 455

Example 3: Input: num = [2,1,5], k = 806 Output: [1,0,2,1] Explanation: 215 + 806 = 1021

Example 4: Input: num = [9,9,9,9,9,9,9,9,9,9], k = 1 Output: [1,0,0,0,0,0,0,0,0,0,0] Explanation: 9999999999 + 1 = 10000000000

Constraints: 1 <= num.length <= 104 0 <= num[i] <= 9 num does not contain any leading zeros except for the zero itself.

1 <= k <= 104

Topics and companies

Topics: Array.

Reported in interviews at Facebook.

How to practise Add to Array-Form of Integer on Thita.ai

Starter code is provided in C, C#, C++, dart, elixir, erlang, Go, Java, JavaScript, Kotlin, PHP, Python, python3, racket, Ruby, Rust, Scala, Swift and TypeScript. Your solution runs against 5 test cases for this problem, with the AI coach available for a hint when you are stuck rather than a finished answer. The reference solution runs in O(n + logk) time and O(1) space.

Open Add to Array-Form of Integer in the code editor, or read the Add to Array-Form of Integer editorial for a worked solution with its approach and complexity analysis.

Where Add to Array-Form of Integer sits in the DSA pattern sheet

• Array/Matrix Manipulation Patterns pattern guide
• Plus One (Handling Carry) subpattern
• The full DSA patterns sheet
• All coding practice problems

Problems related to Add to Array-Form of Integer

Other problems that use the same Plus One (Handling Carry) and Array/Matrix Manipulation Patterns techniques:

• Add Binary — Easy, same subpattern
• Multiply Strings — Medium, same subpattern
• Plus One — Easy, same subpattern
• Diagonal Traverse — Medium, same pattern
• Find All Duplicates in an Array — Medium, same pattern
• Find All Numbers Disappeared in an Array — Easy, same pattern