LeetCode 2667 - Create Hello World Function
The problem asks us to implement a function named createHelloWorld that returns another function. The returned function must always produce the string "Hello World" whenever it is called.
Difficulty: 🟢 Easy
Topics: —
Solution
Problem Understanding
The problem asks us to implement a function named createHelloWorld that returns another function. The returned function must always produce the string "Hello World" whenever it is called.
The important detail is that the returned function may receive any number of arguments, including no arguments at all. Those arguments do not matter and should be completely ignored. Regardless of whether the caller passes integers, objects, arrays, null, or any other values, the returned result must always be exactly "Hello World".
In other words, this problem is testing whether we understand that functions are first class objects in JavaScript and that functions can return other functions. The task is not about processing input values, but about constructing a function with fixed behavior.
The input shown in the examples represents the arguments passed to the returned function, not to createHelloWorld itself. The expected output is always the same constant string.
The constraints state that 0 <= args.length <= 10. This means the returned function may receive anywhere from zero to ten arguments. Since the arguments are ignored entirely, the exact limit does not significantly affect the implementation. The problem is intentionally simple and focuses on understanding closures and function creation.
Several edge cases are important to recognize upfront. The returned function might be called with no arguments, many arguments, or arguments of mixed types. A naive implementation might accidentally depend on the arguments or return something different based on them. However, the problem guarantees that the correct behavior is always to ignore all inputs and return the same string.
Approaches
Brute Force Approach
A brute force interpretation would be to explicitly inspect every argument passed into the returned function and then still return "Hello World" afterward. For example, the function could iterate through all arguments using a loop, examine their values, and then ignore them.
This approach is technically correct because the final returned value remains "Hello World". However, the argument inspection is unnecessary because the problem statement explicitly says the result never changes regardless of the input.
The brute force approach wastes time processing values that have no effect on the answer.
Optimal Approach
The key insight is that the returned function does not depend on any external state or input values. Since the output is always constant, the simplest and most efficient solution is to return a function that immediately returns "Hello World".
No loops, conditionals, or data structures are needed. The returned function can accept arbitrary arguments, but it simply ignores them.
This works because the problem guarantees that the output is invariant across all possible inputs.
| Approach | Time Complexity | Space Complexity | Notes |
|---|---|---|---|
| Brute Force | O(n) | O(1) | Iterates through all arguments before returning the constant string |
| Optimal | O(1) | O(1) | Immediately returns "Hello World" without processing inputs |
Algorithm Walkthrough
- Define the function
createHelloWorld.
This outer function is responsible for creating and returning another function. It does not need to receive or process any input.
2. Inside createHelloWorld, define an inner function.
The inner function represents the function that users will later call. It may accept any number of arguments, but those arguments are irrelevant to the result.
3. Make the inner function return "Hello World".
Since the output is always constant, the function should directly return the string without performing any additional computation.
4. Return the inner function from createHelloWorld.
This allows callers to store the returned function and invoke it later.
Why it works
The algorithm works because the problem requires a constant output independent of input. The returned function ignores all provided arguments and always returns the same string. Since no input can change the result, the implementation is correct for every valid case.
Python Solution
from typing import Any, Callable
class Solution:
def createHelloWorld(self) -> Callable[..., str]:
def hello_world(*args: Any) -> str:
return "Hello World"
return hello_world
The implementation begins by defining the createHelloWorld method. This method returns another function named hello_world.
The hello_world function uses *args so that it can accept any number of arguments of any type. This matches the problem statement, which allows arbitrary inputs to be passed.
Inside the function, we immediately return the string "Hello World". No argument processing is needed because the result is always constant.
Finally, createHelloWorld returns the inner function itself, allowing the caller to invoke it later.
Go Solution
package main
func createHelloWorld() func(...interface{}) string {
return func(args ...interface{}) string {
return "Hello World"
}
}
The Go version follows the same structure as the Python implementation. The outer function returns another function.
Go uses ...interface{} to represent a variadic parameter that can accept any number of values of any type. This is equivalent to Python's *args.
The returned anonymous function ignores all provided arguments and immediately returns "Hello World".
Unlike some problems, there are no concerns about integer overflow, nil handling, or slice manipulation because the arguments are never used.
Worked Examples
Example 1
Input:
args = []
Step by step execution:
- Call
createHelloWorld(). - The function returns the inner function
hello_world. - Invoke
hello_world()with no arguments. - The function immediately returns
"Hello World".
| Step | Action | Result |
|---|---|---|
| 1 | Create returned function | hello_world function created |
| 2 | Call hello_world() |
No arguments received |
| 3 | Return constant string | "Hello World" |
Final output:
"Hello World"
Example 2
Input:
args = [{}, null, 42]
Step by step execution:
- Call
createHelloWorld(). - The function returns the inner function
hello_world. - Invoke
hello_world({}, null, 42). - The arguments are accepted but ignored.
- The function immediately returns
"Hello World".
| Step | Action | Result |
|---|---|---|
| 1 | Create returned function | hello_world function created |
| 2 | Call hello_world({}, null, 42) |
Arguments received |
| 3 | Ignore all arguments | No processing performed |
| 4 | Return constant string | "Hello World" |
Final output:
"Hello World"
Complexity Analysis
| Measure | Complexity | Explanation |
|---|---|---|
| Time | O(1) | The function immediately returns a constant string |
| Space | O(1) | No extra memory proportional to input size is used |
The complexity is constant because the algorithm performs the same fixed amount of work regardless of how many arguments are provided. Even though the function can accept multiple arguments, it does not iterate over or store them.
Test Cases
from typing import Any, Callable
class Solution:
def createHelloWorld(self) -> Callable[..., str]:
def hello_world(*args: Any) -> str:
return "Hello World"
return hello_world
solution = Solution()
f = solution.createHelloWorld()
assert f() == "Hello World" # No arguments
assert f(1) == "Hello World" # Single integer argument
assert f({}, None, 42) == "Hello World" # Mixed argument types
assert f([], [], []) == "Hello World" # Multiple list arguments
assert f("test", True, False) == "Hello World" # String and boolean inputs
assert f(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) == "Hello World" # Maximum argument count
assert f(None) == "Hello World" # None input
assert f({"key": "value"}) == "Hello World" # Dictionary argument
assert f(lambda x: x) == "Hello World" # Function argument
assert f(float("inf"), float("-inf")) == "Hello World" # Special numeric values
| Test | Why |
|---|---|
f() |
Validates behavior with no arguments |
f(1) |
Confirms single values are ignored |
f({}, None, 42) |
Tests mixed data types |
f([], [], []) |
Ensures collections are ignored |
f("test", True, False) |
Tests string and boolean handling |
f(1,2,3,4,5,6,7,8,9,10) |
Verifies maximum argument count |
f(None) |
Confirms null-like values are handled |
f({"key": "value"}) |
Tests dictionary objects |
f(lambda x: x) |
Ensures callable objects do not affect output |
f(float("inf"), float("-inf")) |
Tests unusual numeric values |
Edge Cases
One important edge case is when the returned function is called with no arguments at all. Some implementations might incorrectly expect at least one parameter or attempt to access a missing value. Our implementation handles this correctly because the function does not depend on any arguments and simply returns the constant string.
Another important edge case is when the function receives arguments of many different types simultaneously, such as objects, arrays, booleans, or None. A buggy implementation might accidentally process or stringify these values. Our solution avoids this issue entirely by ignoring all inputs.
A third edge case involves the maximum number of allowed arguments. Even though the constraints permit up to ten arguments, the implementation should behave identically regardless of argument count. Since our solution performs no iteration or processing on the arguments, the runtime remains constant and the behavior is always correct.