codelab: Update Factor lab to match instructions

Uses absl::optional<int> rather than returning a bool and setting an int* arg Change-Id: I7ff642eeb221fe9124ad7018e5aa5d8de3361ec4 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3511035 Auto-Submit: Austin Sullivan <[email protected]> Reviewed-by: Ayu Ishii <[email protected]> Commit-Queue: Ayu Ishii <[email protected]> Cr-Commit-Position: refs/heads/main@{#979287}
azx1573 · Mar 9, 2022 · 131cf84 · 131cf84
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diff --git a/codelabs/cpp101/codelab.md b/codelabs/cpp101/codelab.md
@@ -246,15 +246,14 @@ or `base::PlatformThread::Sleep`).
 
 Take the given (slow) function to find a non-trivial factor of a given integer:
 ```cpp
-bool FindNonTrivialFactor(int n, int* factor) {
-  // Really naive algorithm.
-  for (int i = n-1; i >= 2; --i) {
-    if (n % i == 0) {
-      *factor = i;
-      return true;
-    }
-  }
-  return false;
+absl::optional<int> FindNonTrivialFactor(int n) {
+  // Really naive algorithm.
+  for (int i = 2; i < n; ++i) {
+    if (n % i == 0) {
+      return i;
+    }
+  }
+  return absl::nullopt;
 }
 ```
 Write a command-line utility `factor` that takes a number, posts a task to the

diff --git a/codelabs/cpp101/factor.cc b/codelabs/cpp101/factor.cc
@@ -69,9 +69,9 @@ int main(int argc, char* argv[]) {
 
   absl::optional<int> result;
   // Notice that we're posting the long-running factoring operation to
-  // |base::ThreadPool| to avoid blocking the main thread
+  // `base::ThreadPool` to avoid blocking the main thread.
   //
-  // |run_loop.QuitClosure()| will be called once the factoring task completes.
+  // `run_loop.QuitClosure()` will be called once the factoring task completes.
   base::ThreadPool::PostTaskAndReply(
       FROM_HERE, base::BindOnce(&FindNonTrivialFactorHelper, n, &result),
       run_loop.QuitClosure());