day8

exercises/standard_library_types/iterators1.rs

@@ -8,17 +8,15 @@
 //
 // Execute `rustlings hint iterators1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
-fn main () {
+fn main() {
     let my_fav_fruits = vec!["banana", "custard apple", "avocado", "peach", "raspberry"];
 
-    let mut my_iterable_fav_fruits = ???;   // TODO: Step 1
+    let mut my_iterable_fav_fruits = my_fav_fruits.iter(); // TODO: Step 1
 
     assert_eq!(my_iterable_fav_fruits.next(), Some(&"banana"));
-    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 2
+    assert_eq!(my_iterable_fav_fruits.next(), Some(&"custard apple")); // TODO: Step 2
     assert_eq!(my_iterable_fav_fruits.next(), Some(&"avocado"));
-    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 3
+    assert_eq!(my_iterable_fav_fruits.next(), Some(&"peach")); // TODO: Step 3
     assert_eq!(my_iterable_fav_fruits.next(), Some(&"raspberry"));
-    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 4
+    assert_eq!(my_iterable_fav_fruits.next(), None); // TODO: Step 4
 }

exercises/standard_library_types/iterators2.rs

@@ -2,17 +2,23 @@
 // In this exercise, you'll learn some of the unique advantages that iterators
 // can offer. Follow the steps to complete the exercise.
 // Execute `rustlings hint iterators2` or use the `hint` watch subcommand for a hint.
-
-// I AM NOT DONE
+// Copyright © 2022 matytan. All Rights Reserved.
 
 // Step 1.
 // Complete the `capitalize_first` function.
 // "hello" -> "Hello"
 pub fn capitalize_first(input: &str) -> String {
     let mut c = input.chars();
+    let mut result = String::new();
     match c.next() {
         None => String::new(),
-        Some(first) => ???,
+        Some(first) => {
+            result.push(first.to_ascii_uppercase());
+            for cc in c {
+                result.push(cc)
+            }
+            result
+        }
     }
 }
 
@@ -21,7 +27,7 @@ pub fn capitalize_first(input: &str) -> String {
 // Return a vector of strings.
 // ["hello", "world"] -> ["Hello", "World"]
 pub fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
-    vec![]
+    words.iter().map(|x| capitalize_first(x)).collect()
 }
 
 // Step 3.
@@ -29,7 +35,7 @@ pub fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
 // Return a single string.
 // ["hello", " ", "world"] -> "Hello World"
 pub fn capitalize_words_string(words: &[&str]) -> String {
-    String::new()
+    words.iter().map(|x| capitalize_first(x)).collect()
 }
 
 #[cfg(test)]

exercises/standard_library_types/iterators3.rs

@@ -6,8 +6,6 @@
 //    list_of_results functions.
 // Execute `rustlings hint iterators3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 #[derive(Debug, PartialEq, Eq)]
 pub enum DivisionError {
     NotDivisible(NotDivisibleError),
@@ -22,22 +20,34 @@ pub struct NotDivisibleError {
 
 // Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
 // Otherwise, return a suitable error.
+//判断整除，利用求余数的方法
 pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
-    todo!();
+    // todo!();
+    if b == 0 {
+        Err(DivisionError::DivideByZero)
+    } else if a % b == 0 {
+        //是否整除
+        Ok(a / b)
+    } else {
+        Err(DivisionError::NotDivisible(NotDivisibleError {
+            dividend: a,
+            divisor: b,
+        }))
+    }
 }
 
 // Complete the function and return a value of the correct type so the test passes.
 // Desired output: Ok([1, 11, 1426, 3])
-fn result_with_list() -> () {
+fn result_with_list() -> Result<Vec<i32>, DivisionError> {
     let numbers = vec![27, 297, 38502, 81];
-    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+    numbers.into_iter().map(|n| divide(n, 27)).collect()
 }
 
 // Complete the function and return a value of the correct type so the test passes.
 // Desired output: [Ok(1), Ok(11), Ok(1426), Ok(3)]
-fn list_of_results() -> () {
+fn list_of_results() -> Vec<Result<i32, DivisionError>> {
     let numbers = vec![27, 297, 38502, 81];
-    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+    numbers.into_iter().map(|n| divide(n, 27)).collect()
 }
 
 #[cfg(test)]