1 files changed, 43 insertions, 2 deletions
diff --git a/rustlings/solutions/19_smart_pointers/arc1.rs b/rustlings/solutions/19_smart_pointers/arc1.rs
index dcf2377..bd76189 100644
--- a/rustlings/solutions/19_smart_pointers/arc1.rs
+++ b/rustlings/solutions/19_smart_pointers/arc1.rs
@@ -1,4 +1,45 @@
+// In this exercise, we are given a `Vec` of `u32` called `numbers` with values
+// ranging from 0 to 99. We would like to use this set of numbers within 8
+// different threads simultaneously. Each thread is going to get the sum of
+// every eighth value with an offset.
+//
+// The first thread (offset 0), will sum 0, 8, 16, …
+// The second thread (offset 1), will sum 1, 9, 17, …
+// The third thread (offset 2), will sum 2, 10, 18, …
+// …
+// The eighth thread (offset 7), will sum 7, 15, 23, …
+//
+// Each thread should own a reference-counting pointer to the vector of
+// numbers. But `Rc` isn't thread-safe. Therefore, we need to use `Arc`.
+//
+// Don't get distracted by how threads are spawned and joined. We will practice
+// that later in the exercises about threads.
+
+// Don't change the lines below.
+#![forbid(unused_imports)]
+use std::{sync::Arc, thread};
+
 fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+    let numbers: Vec<_> = (0..100u32).collect();
+
+    let shared_numbers = Arc::new(numbers);
+    //                   ^^^^^^^^^^^^^^^^^
+
+    let mut join_handles = Vec::new();
+
+    for offset in 0..8 {
+        let child_numbers = Arc::clone(&shared_numbers);
+        //                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+        let handle = thread::spawn(move || {
+            let sum: u32 = child_numbers.iter().filter(|&&n| n % 8 == offset).sum();
+            println!("Sum of offset {offset} is {sum}");
+        });
+
+        join_handles.push(handle);
+    }
+
+    for handle in join_handles.into_iter() {
+        handle.join().unwrap();
+    }
 }