How should I practice Checked Recursive Sum?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Headlands Technologies phone screen problems in FastPrep.

Is Checked Recursive Sum associated with Headlands Technologies?

FastPrep tags this as a Headlands Technologies phone screen coding practice problem when the problem catalog has that company and stage context.

Checked Recursive Sum

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Problem statement

Source note: The phone report asks for a recursive sum from1throughn, then discusses a wider long, failure signaling when long cannot be used, and a tail-recursive accumulator for stack overflow. This practice selects the no-wider-type follow-up with a logical signed32-bit result and-1on overflow. The exact width, interface, input limits, balanced-recursion alternative and portable tail-state loop are authored; tail-call optimization is not guaranteed across languages. Approximate source match: 80%. Compatible practice attribution: a separate February 2021 phone report describes a recursive accumulation function, C++ parameter passing and return values, exception-based error handling, recursion stack usage and conversion to a tail-recursive accumulator; the author also mentions template-generated code. That report gives no original callable or numeric domain. The concrete 1-through-n, checked signed-32-bit and -1 conventions here remain authored practice choices tied to the more specific 2023 report; they are not claimed as details of the generic 2021 interview. Template generation is context, not a required implementation, and tail recursion does not guarantee compiler tail-call elimination.

Given a nonnegative integer n, compute the sum of every integer from 1 through n. The sum for n == 0 is 0.

For this exercise, the result must fit in the logical signed 32-bit range from 0 through 2147483647. Return -1 when the exact sum exceeds this range. Do not wrap, clamp or take a modulus. Design checks so no intermediate integer overflows, without relying on a wider integer type.

Implement a recursive summation approach with a safe stack depth, then express the tail-recursive accumulator state as a portable constant-stack loop. A call appearing last in source code does not guarantee that the runtime eliminates its stack frame. The loop preserves the state transition without relying on compiler tail-call optimization.

This interface and the -1 result choose one of the reported follow-up conventions. They do not claim an original interview width, error API or compiler guarantee.

Function

checkedSumUpTo(n: int) → int

Examples

Example 1

n = 5return = 15

The sum is1+2+3+4+5=15.

Example 2

n = 65535return = 2147450880

The exact sum2147450880is below2147483647, so it can be returned as a signed32-bit integer.

Example 3

n = 65536return = -1

The exact sum2147516416exceeds2147483647, so return the authored overflow sentinel-1.

Constraints

0 <= n <= 2147483647.
All inputs are valid. The return type is a logical signed32-bit integer.
If the exact sum fits, return it exactly. Otherwise return -1.
Use checked arithmetic or division comparisons within this logical range; Python arbitrary-size integers and Go machine-sized integers must follow the same explicit result limit.
The interface, zero-input behavior, width and sentinel are authored practice conventions.