RustDay05

HashMap::new()

注意末尾条件,添加足够种类和数量水果即可

// hashmaps1.rs
// A basket of fruits in the form of a hash map needs to be defined.
// The key represents the name of the fruit and the value represents
// how many of that particular fruit is in the basket. You have to put
// at least three different types of fruits (e.g apple, banana, mango)
// in the basket and the total count of all the fruits should be at
// least five.
//
// Make me compile and pass the tests!
//
// Execute `rustlings hint hashmaps1` or use the `hint` watch subcommand for a hint.// I AM NOT DONEuse std::collections::HashMap;fn fruit_basket() -> HashMap<String, u32> {let mut basket = HashMap::new();// TODO: declare your hash map here.// Two bananas are already given for you :)basket.insert(String::from("banana"), 2);// TODO: Put more fruits in your basket here.basket.insert("666".to_string(),3);basket.insert("999".to_string(),1);basket
}#[cfg(test)]
mod tests {use super::*;#[test]fn at_least_three_types_of_fruits() {let basket = fruit_basket();assert!(basket.len() >= 3);}#[test]fn at_least_five_fruits() {let basket = fruit_basket();assert!(basket.values().sum::<u32>() >= 5);}
}

45.hashmap的基础插入操作

注意末尾测试的要求即可

// hashmaps2.rs// A basket of fruits in the form of a hash map is given. The key
// represents the name of the fruit and the value represents how many
// of that particular fruit is in the basket. You have to put *MORE
// THAN 11* fruits in the basket. Three types of fruits - Apple (4),
// Mango (2) and Lychee (5) are already given in the basket. You are
// not allowed to insert any more of these fruits!
//
// Make me pass the tests!
//
// Execute `rustlings hint hashmaps2` or use the `hint` watch subcommand for a hint.// I AM NOT DONEuse std::collections::HashMap;#[derive(Hash, PartialEq, Eq)]
enum Fruit {Apple,Banana,Mango,Lychee,Pineapple,
}fn fruit_basket(basket: &mut HashMap<Fruit, u32>) {let fruit_kinds = vec![Fruit::Apple,Fruit::Banana,Fruit::Mango,Fruit::Lychee,Fruit::Pineapple,];for fruit in fruit_kinds {// TODO: Put new fruits if not already present. Note that you// are not allowed to put any type of fruit that's already// present!}
}#[cfg(test)]
mod tests {use super::*;fn get_fruit_basket() -> HashMap<Fruit, u32> {let mut basket = HashMap::<Fruit, u32>::new();basket.insert(Fruit::Apple, 4);basket.insert(Fruit::Mango, 2);basket.insert(Fruit::Lychee, 5);// at_least_five_types_of_fruits 种类>=5// greater_than_eleven_fruits  总数 >=1basket.insert(Fruit::Banana, 5);basket.insert(Fruit::Pineapple, 5);basket}#[test]fn test_given_fruits_are_not_modified() {let mut basket = get_fruit_basket();fruit_basket(&mut basket);assert_eq!(*(&Fruit::Apple).unwrap(), 4);assert_eq!(*(&Fruit::Mango).unwrap(), 2);assert_eq!(*(&Fruit::Lychee).unwrap(), 5);}#[test]fn at_least_five_types_of_fruits() {let mut basket = get_fruit_basket();fruit_basket(&mut basket);let count_fruit_kinds = basket.len();assert!(count_fruit_kinds >= 5);}#[test]fn greater_than_eleven_fruits() {let mut basket = get_fruit_basket();fruit_basket(&mut basket);let count = basket.values().sum::<u32>();assert!(count > 11);}
}

46.查看hashmap是否包含某个键

这一题有点综合性难度了,我们需要对每场比赛的双方统计得球和失球的次数,然后通过hashMap传递出去

// hashmaps3.rs// A list of scores (one per line) of a soccer match is given. Each line
// is of the form :
// <team_1_name>,<team_2_name>,<team_1_goals>,<team_2_goals>
// Example: England,France,4,2 (England scored 4 goals, France 2).// You have to build a scores table containing the name of the team, goals
// the team scored, and goals the team conceded. One approach to build
// the scores table is to use a Hashmap. The solution is partially
// written to use a Hashmap, complete it to pass the test.// Make me pass the tests!// Execute `rustlings hint hashmaps3` or use the `hint` watch subcommand for a hint.// I AM NOT DONEuse std::collections::HashMap;// A structure to store team name and its goal details.
struct Team {name: String,goals_scored: u8,goals_conceded: u8,
}fn build_scores_table(results: String) -> HashMap<String, Team> {// The name of the team is the key and its associated struct is the value.let mut scores: HashMap<String, Team> = HashMap::new();for r in results.lines() {let v: Vec<&str> = r.split(',').collect();let team_1_name = v[0].to_string();let team_1_score: u8 = v[2].parse().unwrap();let team_2_name = v[1].to_string();let team_2_score: u8 = v[3].parse().unwrap();// TODO: Populate the scores table with details extracted from the// current line. Keep in mind that goals scored by team_1// will be number of goals conceded from team_2, and similarly// goals scored by team_2 will be the number of goals conceded by// team_1.if !ains_key(&team_1_name) {// 创建新用户 都初始化为0scores.insert(team_1_name.clone(),Team{name: team_1_name.clone(),goals_scored: 0,goals_conceded: 0,});};if !ains_key(&team_2_name) {// 创建新用户 都初始化为0scores.insert(team_2_name.clone(),Team{name: team_2_name.clone(),goals_scored: 0,goals_conceded: 0,});};let team1&#_mut(&team_1_name).unwrap();als_scored+=team_1_als_conceded+=team_2_score;let team2&#_mut(&team_2_name).unwrap();als_scored+=team_2_als_conceded+=team_1_score;}scores
}#[cfg(test)]
mod tests {use super::*;fn get_results() -> String {let results = "".to_string()+ "England,France,4,2n"+ "France,Italy,3,1n"+ "Poland,Spain,2,0n"+ "Germany,England,2,1n";results}#[test]fn build_scores() {let scores = build_scores_table(get_results());let mut keys: Vec<&String> = scores.keys().collect();keys.sort();assert_eq!(keys,vec!["England", "France", "Germany", "Italy", "Poland", "Spain"]);}#[test]fn validate_team_score_1() {let scores = build_scores_table(get_results());let team = ("England").unwrap();assert_eq!(als_scored, 5);assert_eq!(als_conceded, 4);}#[test]fn validate_team_score_2() {let scores = build_scores_table(get_results());let team = ("Spain").unwrap();assert_eq!(als_scored, 0);assert_eq!(als_conceded, 2);}
}

47.match通配和转大写/去空白字符/重复添加字符串

对于这样的一个变量

let output = transformer(vec![("hello".into(), Command::Uppercase),(" all roads lead to rome! ".into(), Command::Trim),("foo".into(), Command::Append(1)),("bar".into(), Command::Append(5)),]);

我们需要使用如下形式来定义

Vec<(String,Command)

其中,枚举类型结构如下

pub enum Command {Uppercase,Trim,Append(usize),
}

将字符串转大写 to_uppercase()

output._uppercase())

将字符串首尾空白字符去除

output.im().to_string())

在字符串末尾重复添加特定字符串

output._string()+&"bar".to_string().repeat(*nums))

然后导入my_moduleghegmod里面的公共方法transformer到test里面去即可

// quiz2.rs
// This is a quiz for the following sections:
// - Strings
// - Vecs
// - Move semantics
// - Modules
// - Enums// Let's build a little machine in form of a function.
// As input, we're going to give a list of strings and commands. These commands
// determine what action is going to be applied to the string. It can either be:
// - Uppercase the string
// - Trim the string
// - Append "bar" to the string a specified amount of times
// The exact form of this will be:
// - The input is going to be a Vector of a 2-length tuple,
//   the first element is the string, the second one is the command.
// - The output element is going to be a Vector of strings.
// No hints this time!// I AM NOT DONEpub enum Command {Uppercase,Trim,Append(usize),
}mod my_module {use super::Command;// TODO: Complete the function signature!pub fn transformer(input: Vec<(String,Command)>) -> Vec<String> {// TODO: Complete the output declaration!let mut output: Vec<String>  = vec![];for (string, command) in input.iter() {// TODO: Complete the function body. You can do it!match command {Command::Uppercase => {output._uppercase())}Command::Trim => {output.im().to_string())}Command::Append(nums) =>{output._string()+&"bar".to_string().repeat(*nums))}}}output}
}#[cfg(test)]
mod tests {// TODO: What do we have to import to have `transformer` in scope?use my_module::transformer;use super::Command;#[test]fn it_works() {let output = transformer(vec![("hello".into(), Command::Uppercase),(" all roads lead to rome! ".into(), Command::Trim),("foo".into(), Command::Append(1)),("bar".into(), Command::Append(5)),]);assert_eq!(output[0], "HELLO");assert_eq!(output[1], "all roads lead to rome!");assert_eq!(output[2], "foobar");assert_eq!(output[3], "barbarbarbarbarbar");}
}

48.根据小时来获取冰淇淋的数量

我们首先得知道Option<u16>是一个系统默认枚举类型,其包含Some(nums)和None这两种枚举

我们有两个任务

(1)填补时辰和冰淇淋数量的逻辑关系并对错误的时辰进行特判

(2)对错误的测试样例进行类型修正

我们填写以下逻辑

fn maybe_icecream(time_of_day: u16) -> Option<u16> {// We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a value of 0// The Option output should gracefully handle cases where time_of_day > 23.if (time_of_day<=12) {Some(5)}else if (time_of_day<=24) {Some(0)}else{None}
}

并修改测试样 raw_value的值判断为即可

assert_eq!(icecreams, Some(5));

// options1.rs
// Execute `rustlings hint options1` or use the `hint` watch subcommand for a hint.// I AM NOT DONE// This function returns how much icecream there is left in the fridge.
// If it's before 10PM, there's 5 pieces left. At 10PM, someone eats them
// all, so there'll be no more left :(
// TODO: Return an Option!
fn maybe_icecream(time_of_day: u16) -> Option<u16> {// We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a value of 0// The Option output should gracefully handle cases where time_of_day > 23.if (time_of_day<=12) {Some(5)}else if (time_of_day<=24) {Some(0)}else{None}
}#[cfg(test)]
mod tests {use super::*;#[test]fn check_icecream() {assert_eq!(maybe_icecream(9), Some(5));assert_eq!(maybe_icecream(10), Some(5));assert_eq!(maybe_icecream(23), Some(0));assert_eq!(maybe_icecream(22), Some(0));assert_eq!(maybe_icecream(25), None);}#[test]fn raw_value() {// TODO: Fix this test. How do you get at the value contained in the Option?let icecreams = maybe_icecream(12);assert_eq!(icecreams, Some(5));}
}

48.let type(A)=unknowType(value)的使用

这里面有两个关键语句

let Some(word) = optional_target

let Some(Some(integer)) = optional_integers.pop()

他们的意思是如果等式两边类型相等,

那么就将等式右边的值赋值给等式左边的括号里面的变量

其可以配合if和while使用 ,也可以使用花括号对后续进行操作

// options2.rs
// Execute `rustlings hint options2` or use the `hint` watch subcommand for a hint.// I AM NOT DONE#[cfg(test)]
mod tests {use super::*;#[test]fn simple_option() {let target = "rustlings";let optional_target = Some(target);// TODO: Make this an if let statement whose value is "Some" typeif let Some(word) = optional_target {assert_eq!(word, target);}}#[test]fn layered_option() {let mut range = 10;let mut optional_integers: Vec<Option<i8>> = Vec::new();for i in 0..(range + 1) {optional_integers.push(Some(i));}// TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>// You can stack `Option<T>`'s into while let and if letwhile let Some(Some(integer)) = optional_integers.pop() {assert_eq!(integer, range);range -= 1;}}
}

49.将引用传递给match避免产生所有权转让

// options3.rs
// Execute `rustlings hint options3` or use the `hint` watch subcommand for a hint.// I AM NOT DONEstruct Point {x: i32,y: i32,
}fn main() {let y: Option<Point> = Some(Point { x: 100, y: 200 });match &y {Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),_ => println!("no match"),}y; // Fix without deleting this line.
}

50.错误类型处理

处理事物错误与否,我们要使用Result<String,String>枚举类型

其包含Ok(value)和Err(value)这两种枚举

Result<String,String>代表正确时返回Ok(String),错误时返回Err(String)

// errors1.rs
// This function refuses to generate text to be printed on a nametag if
// you pass it an empty string. It'd be nicer if it explained what the problem
// was, instead of just sometimes returning `None`. Thankfully, Rust has a similar
// construct to `Option` that can be used to express error conditions. Let's use it!
// Execute `rustlings hint errors1` or use the `hint` watch subcommand for a hint.// I AM NOT DONEpub fn generate_nametag_text(name: String) -> Result<String,String> {if name.is_empty() {// Empty names aren't allowed.// NoneErr("`name` was empty; it must be nonempty.".into())} else {Ok(format!("Hi! My name is {}", name))}
}#[cfg(test)]
mod tests {use super::*;#[test]fn generates_nametag_text_for_a_nonempty_name() {assert_eq!(generate_nametag_text("Beyoncé".into()),Ok("Hi! My name is Beyoncé".into()));}#[test]fn explains_why_generating_nametag_text_fails() {assert_eq!(generate_nametag_text("".into()),// Don't change this lineErr("`name` was empty; it must be nonempty.".into()));}
}