5 files changed, 74 insertions, 4 deletions
diff --git a/exercises/strings/mod.rs b/exercises/strings/mod.rs
deleted file mode 100644
index b1b460b..0000000
--- a/exercises/strings/mod.rs
+++ /dev/null
@@ -1,2 +0,0 @@
-mod strings1;
-mod strings2;
diff --git a/exercises/strings/strings1.rs b/exercises/strings/strings1.rs
index 8090244..0de86a1 100644
--- a/exercises/strings/strings1.rs
+++ b/exercises/strings/strings1.rs
@@ -1,6 +1,6 @@
 // strings1.rs
 // Make me compile without changing the function signature!
-// Execute `rustlings hint strings1` for hints ;)
+// Execute `rustlings hint strings1` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE
 
diff --git a/exercises/strings/strings2.rs b/exercises/strings/strings2.rs
index 5a2ce74..0c48ec9 100644
--- a/exercises/strings/strings2.rs
+++ b/exercises/strings/strings2.rs
@@ -1,6 +1,6 @@
 // strings2.rs
 // Make me compile without changing the function signature!
-// Execute `rustlings hint strings2` for hints :)
+// Execute `rustlings hint strings2` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE
 
diff --git a/exercises/strings/strings3.rs b/exercises/strings/strings3.rs
new file mode 100644
index 0000000..9e25d30
--- /dev/null
+++ b/exercises/strings/strings3.rs
@@ -0,0 +1,43 @@
+// strings3.rs
+// Execute `rustlings hint strings3` or use the `hint` watch subcommand for a hint.
+
+// I AM NOT DONE
+
+fn trim_me(input: &str) -> String {
+    // TODO: Remove whitespace from the end of a string!
+    ???
+}
+
+fn compose_me(input: &str) -> String {
+    // TODO: Add " world!" to the string! There's multiple ways to do this!
+    ???
+}
+
+fn replace_me(input: &str) -> String {
+    // TODO: Replace "cars" in the string with "balloons"!
+    ???
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn trim_a_string() {
+        assert_eq!(trim_me("Hello!     "), "Hello!");
+        assert_eq!(trim_me("  What's up!"), "What's up!");
+        assert_eq!(trim_me("   Hola!  "), "Hola!");
+    }
+
+    #[test]
+    fn compose_a_string() {
+        assert_eq!(compose_me("Hello"), "Hello world!");
+        assert_eq!(compose_me("Goodbye"), "Goodbye world!");
+    }
+
+    #[test]
+    fn replace_a_string() {
+        assert_eq!(replace_me("I think cars are cool"), "I think balloons are cool");
+        assert_eq!(replace_me("I love to look at cars"), "I love to look at balloons");
+    }
+}
diff --git a/exercises/strings/strings4.rs b/exercises/strings/strings4.rs
new file mode 100644
index 0000000..c410b56
--- /dev/null
+++ b/exercises/strings/strings4.rs
@@ -0,0 +1,29 @@
+// strings4.rs
+
+// Ok, here are a bunch of values-- some are `String`s, some are `&str`s. Your
+// task is to call one of these two functions on each value depending on what
+// you think each value is. That is, add either `string_slice` or `string`
+// before the parentheses on each line. If you're right, it will compile!
+// No hints this time!
+
+// I AM NOT DONE
+
+fn string_slice(arg: &str) {
+    println!("{}", arg);
+}
+fn string(arg: String) {
+    println!("{}", arg);
+}
+
+fn main() {
+    ???("blue");
+    ???("red".to_string());
+    ???(String::from("hi"));
+    ???("rust is fun!".to_owned());
+    ???("nice weather".into());
+    ???(format!("Interpolation {}", "Station"));
+    ???(&String::from("abc")[0..1]);
+    ???("  hello there ".trim());
+    ???("Happy Monday!".to_string().replace("Mon", "Tues"));
+    ???("mY sHiFt KeY iS sTiCkY".to_lowercase());
+}