Solution Review: Concatenate Words Starting With 'c'

This lesson gives a detailed solution review of the challenge in the previous lesson.

We'll cover the following


fn test(my_str:String)-> String {
let mut my_updated_string = "".to_string();
for word in my_str.split(" "){
if word.starts_with("c"){
my_updated_string.push(' ');
fn main(){
let my_str= "This is a comprehensive course in Rust programming language on Educative. Read it with full concentration to grasp the content of the course";
println!("Original String: {}", my_str);
let updated_string = test(my_str.to_string());
println!("Updated String: {}", updated_string);


  • On line 1, a String object my_str is passed as an argument.

  • On line 2, my_updated_string of type String is initialized with the value null.

  • On line 3, the string is traversed using a for loop that splits on whitespace using the .split method.

    • On line 4 to line 7, within the for loop, an if condition checks if the starting letter of the word (splitted on space) is c using the starts_with() method, then
      • appends the word in my_updated_string on line 5.
      • appends the space in my_updated_string on line 6.
  • On line 9, the appended space at the end is removed by using the pop function.

  • After the loop terminates the variable my_updated_string() is returned.

The following illustration explains the above concept:

The string is shortened just to give you an idea of how this code executes.

Now that you have learned about Strings, let’s learn about a growable array called “Vectors” in the next chapter.

Create a free account to access the full course.

Learn to code, grow your skills, and succeed in your tech interview

By signing up, you agree to Educative's Terms of Service and Privacy Policy