Create Hello World Function
Asked at Microsoft
Problem
Create a function that returns "Hello World" every time it is called. This is a fundamental closure and function-scoping question used in early rounds to test your understanding of how functions capture their environment.
Asked At
| Company | Difficulty | |
|---|---|---|
| Microsoft | Easy | View all Microsoft questions → |
How to Think About It
The simplest approach: define a function that returns the string "Hello World". No parameters, no state. Every call returns the same value. O(1) time and space.
In JavaScript, use a closure: function createHelloWorld() { return function(...args) { return "Hello World"; }; }. The inner function closes over nothing but still works because the string is a literal.
In Python: def createHelloWorld(): return lambda *args: "Hello World". The lambda is a closure that captures nothing from the outer scope - it just returns a constant.
Why this question exists: interviewers want to see if you understand first-class functions, closures, and the difference between defining a function and calling it. Returning a function vs returning the result of a function.
Edge cases: ensure the function works regardless of the number or type of arguments passed. The function should always return the exact string "Hello World" (capital H, capital W, space in between).
The trick is that the inner function accepts arguments (via *args or ...args) but ignores them. The signature requires it to be callable with any arguments, but the return value is always "Hello World".
createHelloWorld()() → "Hello World"
createHelloWorld()(1, 2, 3) → "Hello World"
createHelloWorld()("anything") → "Hello World"
Optimal Approach
Step 1: Define an outer function createHelloWorld.
Step 2: Inside it, define and return an inner function that takes any number of arguments.
Step 3: The inner function simply returns the string "Hello World".
The key concept is closures: the inner function is a first-class value that can be returned and later called. The returned function ignores all arguments.
Walkthrough:fn = createHelloWorld() - creates the closure, returns the inner functionfn() → "Hello World"fn(1, 2, 3) → "Hello World"fn("any", "args") → "Hello World"
Time: O(1). Space: O(1).
What Trips People Up in Real Interviews
Returning "Hello World" directly instead of returning a function. The question asks you to create a function that returns another function. createHelloWorld() should return a callable, not a string.
Not handling extra arguments. The inner function must accept any number of arguments (even if it ignores them). Use *args in Python or ...args in JavaScript.
Overcomplicating with a class or closure state. This question is intentionally simple - just return a function that returns a constant string.
Forgetting the exact string format. It must be "Hello World" with capital H and W. Not "hello world" or "Hello world".
Confusing this with a class-based design pattern. While you could use a class with __call__, the simplest solution is a nested function or lambda.
Solution Code
def createHelloWorld():
return lambda *args: "Hello World"Frequently Asked Questions
What is the Create Hello World Function problem?
Create a function that returns "Hello World" every time it is called. This is a fundamental closure and function-scoping question used in early rounds to test your understanding of how functions capture their environment.
How do you solve Create Hello World Function?
The optimal approach is described in detail above, including step-by-step walkthroughs, complexity analysis, and solution code in Python. Scroll up to the "Optimal Approach" section.
What companies ask Create Hello World Function?
Create Hello World Function is asked at Microsoft. It is a easy difficulty problem.
What are common mistakes on Create Hello World Function?
- Returning "Hello World" directly instead of returning a function. The question asks you to create a function that returns another function. `createHelloWorld()` should return a callable, not a string.
- Not handling extra arguments. The inner function must accept any number of arguments (even if it ignores them). Use `*args` in Python or `...args` in JavaScript.
- Overcomplicating with a class or closure state. This question is intentionally simple - just return a function that returns a constant string.
- Forgetting the exact string format. It must be "Hello World" with capital H and W. Not "hello world" or "Hello world".
- Confusing this with a class-based design pattern. While you could use a class with `__call__`, the simplest solution is a nested function or lambda.