Create Hello World Function - Solution & Explanation
Problem Statement
createHelloWorld. It should return a new function that always returns "Hello World".
Example 1:
Input: args = [] Output: "Hello World" Explanation: const f = createHelloWorld(); f(); // "Hello World" The function returned by createHelloWorld should always return "Hello World".
Example 2:
Input: args = [{},null,42]
Output: "Hello World"
Explanation:
const f = createHelloWorld();
f({}, null, 42); // "Hello World"
Any arguments could be passed to the function but it should still always return "Hello World".
Constraints:
0 <= args.length <= 10
Approach Overview
Problem Overview: You need to implement a function that returns another function. When the returned function is executed, it must return the string "Hello World". The task focuses on understanding basic function construction and how returned functions behave.
Approach 1: Closure Approach (O(1) time, O(1) space)
This method returns an inner function that produces the string "Hello World" when called. The outer function creates the inner function and returns it as a closure. Closures allow a function to capture variables from its surrounding scope, although in this case no external variable is required. The key operation is returning a function reference rather than executing it immediately. This pattern appears frequently in JavaScript and functional programming tasks involving callbacks, factories, and higher‑order functions. Related concepts appear in closures and functions.
Approach 2: Direct Return Approach (O(1) time, O(1) space)
The direct return method simply returns a function whose body returns "Hello World". Instead of explicitly constructing additional logic, the function immediately defines and returns the inner function. The implementation is minimal: define a function literal and return the constant string from it. This approach works in most languages that support returning functions or lambdas. It demonstrates how higher‑order functions operate in languages like JavaScript and Python.
Recommended for interviews: Interviewers expect the direct return approach because it clearly demonstrates that you understand higher‑order functions and returning callable objects. The closure approach still shows useful knowledge about function scope and closures, which often appear in callback patterns and functional design. Both solutions run in constant time and space, but writing the minimal version shows clean thinking and familiarity with function syntax.
Approach 1: Closure Approach
This approach uses the concept of closures to return a function that ignores its arguments and always returns the string 'Hello World'. In this method, createHelloWorld returns a new function that consistently returns the string when invoked.
In C, we use a function createHelloWorld that simply returns the string "Hello World". We then define a function pointer type hello_function to point to such functions and return it through another function getHelloWorldFunction.
Complexity
Time Complexity: O(1) as the function performs a constant-time operation.
Space Complexity: O(1) since it doesn't use any extra space dependent on input size.
Approach 2: Direct Return Approach
This approach directly returns a function without using intermediate variables like closures. The returned function will always output 'Hello World', ignoring any provided arguments.
In C, we create a simple function returnHelloWorld that directly returns the string "Hello World". This can be used in place of closures as C lacks native closure support.
Complexity
Time Complexity: O(1). The function executes a single return instruction.
Space Complexity: O(1) as there are no dynamic allocations.
Approach 3: Default Approach
Code
TypeScript
Complexity Comparison
| Approach | Complexity |
|---|---|
| Closure Approach | Time Complexity: O(1) as the function performs a constant-time operation. |
| Direct Return Approach | Time Complexity: O(1). The function executes a single return instruction. |
| Default Approach | — |
Detailed Complexity Analysis
| Approach | Time | Space | When to Use |
|---|---|---|---|
| Closure Approach | O(1) | O(1) | When demonstrating closures or higher‑order function behavior |
| Direct Return Approach | O(1) | O(1) | Preferred minimal solution when a simple function return is required |
Video Solution
Create Hello World Function (Closure - Day1) - Leetcode 2667 - JavaScript 30-Day Challenge • NeetCodeIO • 130,461 views views
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