Challenge 3: Range-Based for as Sugar Over the Explicit Iterator Loop — Possible Solution
====================================================================

The range-based for loop is called "sugar" because it doesn't
introduce any genuinely new capability the language couldn't already
express -- it's purely a more convenient SYNTAX that the compiler
mechanically translates into the exact explicit-iterator pattern this
chapter opened with. Writing `for (auto x : container)` and writing
out `for (auto it = container.begin(); it != container.end(); ++it) {
auto x = *it; ... }` produce, under the hood, essentially the same
generated code -- the range-based version simply hides the
begin()/end()/++it/*it bookkeeping the programmer would otherwise have
to spell out by hand every single time.

Example rewrite:

Range-based for:

    std::vector<int> nums = {1, 2, 3};
    for (auto x : nums) {
        std::cout << x << std::endl;
    }

Equivalent explicit iterator-based form:

    std::vector<int> nums = {1, 2, 3};
    for (auto it = nums.begin(); it != nums.end(); ++it) {
        auto x = *it;
        std::cout << x << std::endl;
    }

Both print the identical output (1, 2, 3, each on its own line) --
confirming the range-based version is a genuine shorthand for exactly
this iterator pattern, not a separate mechanism.

WHY THIS WORKS AS AN ANSWER
------------------------------
This explains precisely what "sugar" means here (a syntax translation
to the SAME underlying mechanism, not new capability) and demonstrates
it concretely with a matched pair of loops producing identical output,
rather than asserting the equivalence without showing it.