First working solution for rust/magazine-cutout

Author: EphemeralDev

rust/magazine-cutout/.gitignore

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+# Generated by Cargo
+# will have compiled files and executables
+/target/
+**/*.rs.bk
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here http://doc.crates.io/guide.html#cargotoml-vs-cargolock
+Cargo.lock

rust/magazine-cutout/Cargo.toml

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+[package]
+name = "magazine_cutout"
+version = "0.1.0"
+edition = "2021"

rust/magazine-cutout/HINTS.md

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+# Hints
+
+## General
+
+- Upon fetching an entry using the `entry` method, the entry can be modified in-place after dereferencing it.
+
+- The `or_insert` [method](https://doc.rust-lang.org/std/collections/hash_map/enum.Entry.html#method.or_insert) inserts the given value in the case when the entry is vacant, and returns a mutable reference to the value in the entry.
+
+```rust
+*counter.entry(key).or_insert(0) += 1;
+```
+
+- The `or_default` [method](https://doc.rust-lang.org/std/collections/hash_map/enum.Entry.html#method.or_default) ensures a value is in the entry by inserting the default value if empty, and returns a mutable reference to the value in the entry.
+
+```rust
+*counter.entry(key).or_default() += 1;
+```

rust/magazine-cutout/README.md

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+# Magazine Cutout
+
+Welcome to Magazine Cutout on Exercism's Rust Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+If you get stuck on the exercise, check out `HINTS.md`, but try and solve it without using those first :)
+
+## Introduction
+
+Rust's entry API provides a view into a single entry in map, which may be either a `HashMap` or a `BTreeMap`.
+The entry may be either occupied or vacant, and the API provides methods to modify the contents of the entry.
+
+## Instructions
+
+In this exercise you'll be using a `HashMap`, along with entry API methods, to solve a simple algorithm problem.
+
+Given `&[&str]` representing the words of a magazine article, and `&[&str]` representing the words of a note you would like to send, can you compose your note by cutting words out of the magazine and pasting them into a letter?
+
+Notes:
+
+- This implies physical cutting and pasting; the magazine needs to contain at least as many copies of each word as the note requires.
+- Capitalization matters; just because you're pasting together a note composed from words of a magazine doesn't mean you're willing to be ungrammatical.
+
+You'll start with the following stubbed function signature:
+
+```rust
+pub fn can_construct_note(magazine: &[&str], note: &[&str]) -> bool {
+    unimplemented!()
+}
+```
+
+Given the following input
+
+```rust
+let magazine = "two times three is not four".split_whitespace().collect::<Vec<&str>>();
+let note = "two times two is four".split_whitespace().collect::<Vec<&str>>();
+assert!(!can_construct_note(&magazine, &note));
+```
+
+The function returns `false` since the magazine only contains one instance of `"two"` when the note requires two of them.
+
+The following input will succeed: 
+
+```rust
+let magazine = "Astronomer Amy Mainzer spent hours chatting with Leonardo DiCaprio for Netflix's 'Don't Look Up'".split_whitespace().collect::<Vec<&str>>();
+let note = "Amy Mainzer chatting with Leonardo DiCaprio"
+    .split_whitespace()
+    .collect::<Vec<&str>>();
+assert!(can_construct_note(&magazine, &note));
+```
+
+The function returns `true` since the magazine contains all the words that the note requires.
+
+## Source
+
+### Created by
+
+- @seanchen1991

rust/magazine-cutout/src/lib.rs

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+use std::collections::HashMap;
+
+pub fn can_construct_note(magazine: &[&str], note: &[&str]) -> bool {
+    let mut map = HashMap::new();
+
+    for word in magazine {
+        *map.entry(word).or_insert(0) += 1;
+    }
+
+    for word in note {
+        *map.entry(word).or_insert(0) -= 1;
+
+        if map.values().any(|&k| k < 0) {
+            return false;
+        }
+    }
+    true
+}

rust/magazine-cutout/tests/magazine-cutout.rs

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+use magazine_cutout::*;
+
+#[test]
+fn test_magazine_has_fewer_words_available_than_needed() {
+    let magazine = "two times three is not four"
+        .split_whitespace()
+        .collect::<Vec<&str>>();
+    let note = "two times two is four"
+        .split_whitespace()
+        .collect::<Vec<&str>>();
+    assert!(!can_construct_note(&magazine, &note));
+}
+
+#[test]
+#[ignore]
+fn test_fn_returns_true_for_good_input() {
+    let magazine = "The metro orchestra unveiled its new grand piano today. Its donor paraphrased Nathn Hale: \"I only regret that I have but one to give \"".split_whitespace().collect::<Vec<&str>>();
+    let note = "give one grand today."
+        .split_whitespace()
+        .collect::<Vec<&str>>();
+    assert!(can_construct_note(&magazine, &note));
+}
+
+#[test]
+#[ignore]
+fn test_fn_returns_false_for_bad_input() {
+    let magazine = "I've got a lovely bunch of coconuts."
+        .split_whitespace()
+        .collect::<Vec<&str>>();
+    let note = "I've got som coconuts"
+        .split_whitespace()
+        .collect::<Vec<&str>>();
+    assert!(!can_construct_note(&magazine, &note));
+}
+
+#[test]
+#[ignore]
+fn test_case_sensitivity() {
+    let magazine = "i've got some lovely coconuts"
+        .split_whitespace()
+        .collect::<Vec<&str>>();
+    let note = "I've got some coconuts"
+        .split_whitespace()
+        .collect::<Vec<&str>>();
+    assert!(!can_construct_note(&magazine, &note));
+
+    let magazine = "I've got some lovely coconuts"
+        .split_whitespace()
+        .collect::<Vec<&str>>();
+    let note = "i've got some coconuts"
+        .split_whitespace()
+        .collect::<Vec<&str>>();
+    assert!(!can_construct_note(&magazine, &note));
+}
+
+#[test]
+#[ignore]
+fn test_magazine_has_more_words_available_than_needed() {
+    let magazine = "Enough is enough when enough is enough"
+        .split_whitespace()
+        .collect::<Vec<&str>>();
+    let note = "enough is enough".split_whitespace().collect::<Vec<&str>>();
+    assert!(can_construct_note(&magazine, &note));
+}
+
+#[test]
+#[ignore]
+fn test_magazine_has_one_good_word_many_times_but_still_cant_construct() {
+    let magazine = "A A A".split_whitespace().collect::<Vec<&str>>();
+    let note = "A nice day".split_whitespace().collect::<Vec<&str>>();
+    assert!(!can_construct_note(&magazine, &note));
+}