giscus[bot]
bot Apr 16, 2022

// 填空
fn main() {
 // array -> Vec
 // impl From<[T; N]> for Vec
 let arr = [1, 2, 3];
 let v1 = Vec::from(arr);
 let v2: Vec<i32> = arr.into();
 
 assert_eq!(v1, v2);
 
 
 // String -> Vec
 // impl From<String> for Vec
 let s = "hello".to_string();
 let v1: Vec<u8> = s.into();
 let s = "hello".to_string();
 let v2 = s.into_bytes();
 assert_eq!(v1, v2);
 // impl<'_> From<&'_ str> for Vec
 let s = "hello";
 let v3 = Vec::from(s);
 assert_eq!(v2, v3);
 // 迭代器 Iterators 可以通过 collect 变成 Vec
 let v4: Vec<i32> = [0; 10].iter().map(|x| *x).collect();
 assert_eq!(v4, vec![0; 10]);
 println!("Success!")
 }

1 reply

@flasco giscus

flasco Dec 6, 2022 — with giscus

第五题

// 修复错误
fn main() {
 let mut v = vec![1, 2, 3];
 let slice1 = &v[..];
 // 越界访问将导致 panic.
 // 修改时必须使用 `v.len`
 let slice2 = &v[0..v.len()];
 
 assert_eq!(slice1, slice2);
 
 // 切片是只读的
 // 注意:切片和 `&Vec` 是不同的类型,后者仅仅是 `Vec` 的引用,并可以通过解引用直接获取 `Vec`
 let vec_ref: &mut Vec<i32> = &mut v;
 (*vec_ref).push(4);
 let mut slice3: Vec<i32> = Vec::from(&v[..3]);
 slice3.push(4);
 assert_eq!(slice3, &[1, 2, 3, 4]);
 println!("Success!")
}

Bruce012356
Jan 6, 2023 — with giscus

mark

0 replies

Nixicodo
Mar 2, 2023 — with giscus

第四题我的做法。忘了用if let了,会比match更简洁。

fn main() {
 let mut v = Vec::from([1, 2, 3]);
 for i in 0..5 {
 match v.get(i)
 {
 Some(num)=>{
 println!("{:?}", num);
 v[i]=num+1;
 },
 None=>v.push(i+2)
 }
 
 }
 assert_eq!(v, vec![2, 3, 4, 5, 6]);
 println!("Success!")
}`

1 reply

@QIN2DIM giscus

QIN2DIM Jun 27, 2023 — with giscus

fn main() {
 let mut v = Vec::from([1, 2, 3]);
 for i in 0..5 {
 if let Some(num) = v.get(i) {
 println!("{:?}", num);
 v[i] = num + 1;
 } else {
 v.push(i + 2)
 }
 }
 assert_eq!(v, vec![2, 3, 4, 5, 6]);
 println!("Success!")
}

XU0618
May 3, 2023 — with giscus

lala

0 replies

Ghy0202
Jul 18, 2023 — with giscus

1、回顾一下对于Vec的遍历,以及其所有权

fn main() {
 let arr: [u8; 3] = [1, 2, 3];
 
 let v = Vec::from(arr);
 is_vec(v.clone());
 let v = vec![1, 2, 3];
 is_vec(v.clone());
 // vec!(..) 和 vec![..] 是同样的宏,宏可以使用 []、()、{}三种形式,因此...
 let v = vec!(1, 2, 3);
 is_vec(v.clone());
 
 // ...在下面的代码中, v 是 Vec<[u8; 3]> , 而不是 Vec<u8>
 // 使用 Vec::new 和 `for` 来重写下面这段代码
 let mut v1=Vec::new();
 for a in arr{
 v1.push(a);
 }
 is_vec(v1.clone());
 
 assert_eq!(v, v1);
 println!("Success!")
}
fn is_vec(v: Vec<u8>) {}

2、Vec可以用extend来进行拓展

fn main() {
 let mut v1 = Vec::from([1, 2, 4]);
 v1.pop();
 v1.push(3);
 
 let mut v2 = Vec::new();
 v2.extend(v1.clone());//这里不clone的话会导致v1失去所有权
 assert_eq!(v1, v2);
 println!("Success!")
}

3、array可以通过.into()变成Vec,或者使用Vec::from()进行转换;Iterator可以通过collect变成 Vec

fn main() {
 // array -> Vec
 // impl From<[T; N]> for Vec
 let arr = [1, 2, 3];
 let v1 = Vec::from(arr);
 let v2: Vec<i32> = arr.into();
 
 assert_eq!(v1, v2);
 // String -> Vec
 // impl From<String> for Vec
 let s = "hello".to_string();
 let v1: Vec<u8> = s.into();
 let s = "hello".to_string();
 let v2 = s.into_bytes();
 assert_eq!(v1, v2);
 // impl<'_> From<&'_ str> for Vec
 let s = "hello";
 let v3 = Vec::from(s);
 assert_eq!(v2, v3);
 // 迭代器 Iterators 可以通过 collect 变成 Vec
 let v4: Vec<i32> = [0; 10].into_iter().collect();
 assert_eq!(v4, vec![0; 10]);
 println!("Success!")
 }

4、索引

fn main() {
 let mut v = Vec::from([1, 2, 3]);
 for i in 0..3 {
 println!("{:?}", v[i])
 }
 for i in 0..5 {
 // 实现这里的代码...
 if i<=2{
 v[i]+=1;
 }else{
 v.push(i+2);
 }
 }
 assert_eq!(v, vec![2, 3, 4, 5, 6]);
 println!("Success!")
}

5、Vec中的切片

fn main() {
 let mut v = vec![1, 2, 3];
 let slice1 = &v[..];
 // 越界访问将导致 panic.
 // 修改时必须使用 `v.len`
 let slice2 = &v[0..v.len()];
 
 assert_eq!(slice1, slice2);
 
 // 切片是只读的
 // 注意:切片和 `&Vec` 是不同的类型,后者仅仅是 `Vec` 的引用,并可以通过解引用直接获取 `Vec`
 let vec_ref: &mut Vec<i32> = &mut v;
 (*vec_ref).push(4);
 let slice3 = &vec_ref[0..4];
 //slice3.push(4);
 assert_eq!(slice3, &[1, 2, 3, 4]);
 println!("Success!")
}

6、len和capacity的区别

fn main() {
 let mut vec = Vec::with_capacity(10);
 assert_eq!(vec.len(), 0);
 assert_eq!(vec.capacity(), 10);
 // 由于提前设置了足够的容量,这里的循环不会造成任何内存分配...
 for i in 0..10 {
 vec.push(i);
 }
 assert_eq!(vec.len(), 10);
 assert_eq!(vec.capacity(), 10);
 // ...但是下面的代码会造成新的内存分配
 vec.push(11);
 assert_eq!(vec.len(), 11);
 assert!(vec.capacity() >= 11);
 // 填写一个合适的值,在 `for` 循环运行的过程中,不会造成任何内存分配
 let mut vec = Vec::with_capacity(100);
 for i in 0..100 {
 vec.push(i);
 }
 assert_eq!(vec.len(),100);
 assert_eq!(vec.capacity(), 100);
 
 println!("Success!")
}

7、用枚举对象在Vec中存储不同的类型

#[derive(Debug,PartialEq)]//注意此处需要实现PartialEq
enum IpAddr {
 V4(String),
 V6(String),
}
fn main() {
 // 填空
 let v : Vec<IpAddr>= Vec::from([
 IpAddr::V4("127.0.0.1".to_string()),
 IpAddr::V6("::1".to_string())
 ]);
 
 // 枚举的比较需要派生 PartialEq 特征
 assert_eq!(v[0], IpAddr::V4("127.0.0.1".to_string()));
 assert_eq!(v[1], IpAddr::V6("::1".to_string()));
 println!("Success!")
}

8、实现同一个特征的可以用Box封装起来,然后作为同一个Vec元素

trait IpAddr {
 fn display(&self);
}
struct V4(String);
impl IpAddr for V4 {
 fn display(&self) {
 println!("ipv4: {:?}",self.0)
 }
}
struct V6(String);
impl IpAddr for V6 {
 fn display(&self) {
 println!("ipv6: {:?}",self.0)
 }
}
fn main() {
 // 填空
 let v: Vec<Box<dyn IpAddr>>= vec![
 Box::new(V4("127.0.0.1".to_string())),
 Box::new(V6("::1".to_string())),
 ];
 for ip in v {
 ip.display();
 }
}

0 replies

chenhai998
Aug 6, 2023 — with giscus

done

0 replies

yuliang0225
Dec 24, 2023 — with giscus

7好阴哦

0 replies

CynicalHeart
Dec 24, 2023 — with giscus

到这期确实变难了不少。

0 replies

pypanta
Jan 19, 2024 — with giscus

let v4: Vec<i32> = [0; 10].into_iter().collect();

This will produce error:

value of type `Vec<i32>` cannot be built from `std::iter::Iterator<Item=&{integer}>`

Solutions:

let v4: Vec<i32> = [0; 10].iter().copied().collect(); -> https://stackoverflow.com/a/64200786

Or:

let v4: Vec<i32> = IntoIterator::into_iter([0; 10]).collect();

0 replies

BokutoMan
Feb 22, 2024 — with giscus

down

0 replies

felipe300
Feb 29, 2024 — with giscus

done

0 replies

ldd19920711
Mar 3, 2024 — with giscus

mark 11.2 5

0 replies

DylanJinx
May 10, 2024 — with giscus

done~~~

0 replies

TDAkory
Jul 20, 2024 — with giscus

mark finished

0 replies

DataShare-duo
Sep 26, 2024 — with giscus

难起来了

0 replies

bansal-harsh-2504
Dec 18, 2024 — with giscus

Day 9
Done✅

0 replies

gastrodia
Jan 10, 2025 — with giscus

第一题

fn main() {
 let arr: [u8; 3] = [1, 2, 3];
 let v = Vec::from(arr);
 is_vec(&v);
 let v = vec![1, 2, 3];
 is_vec(&v);
 // vec!(..) 和 vec![..] 是同样的宏,宏可以使用 []、()、{}三种形式,因此...
 let v = vec!(1, 2, 3);
 is_vec(&v);
 // ...在下面的代码中, v 是 Vec<[u8; 3]> , 而不是 Vec<u8>
 // 使用 Vec::new 和 `for` 来重写下面这段代码
 // let v1 = vec!(arr);
 let mut v1 = Vec::new();
 for i in &arr {
 v1.push(*i);
 }
 is_vec(&v1);
 assert_eq!(v, v1);
 println!("Success!")
}
fn is_vec(v: &Vec<u8>) {}

第二题

// 填空
fn main() {
 let mut v1 = Vec::from([1, 2, 4]);
 v1.pop();
 v1.push(3);
 let mut v2 = Vec::new();
 v2.extend([1,2,3]);
 assert_eq!(v1, v2);
 println!("Success!")
}

第三题

// 填空
fn main() {
 // array -> Vec
 // impl From<[T; N]> for Vec
 let arr = [1, 2, 3];
 let v1 = Vec::from(arr);
 let v2: Vec<i32> = arr.to_vec();
 assert_eq!(v1, v2);
 // String -> Vec
 // impl From<String> for Vec
 let s = "hello".to_string();
 let v1: Vec<u8> = s.into();
 let s = "hello".to_string();
 let v2 = s.into_bytes();
 assert_eq!(v1, v2);
 // impl<'_> From<&'_ str> for Vec
 let s = "hello";
 let v3 = Vec::from(s);
 assert_eq!(v2, v3);
 // 迭代器 Iterators 可以通过 collect 变成 Vec
 let v4: Vec<i32> = [0; 10].into_iter().collect();
 assert_eq!(v4, vec![0; 10]);
 println!("Success!")
}

第四题

// 修复错误并实现缺失的代码
fn main() {
 let mut v = Vec::from([1, 2, 3]);
 for i in 0..3 {
 println!("{:?}", v[i])
 }
 v.clear();
 for i in 2..7 {
 // 实现这里的代码...
 v.push(i);
 }
 assert_eq!(v, vec![2, 3, 4, 5, 6]);
 println!("Success!")
}

第五题

// 修复错误
fn main() {
 let mut v = vec![1, 2, 3];
 let slice1 = &v[..];
 // 越界访问将导致 panic.
 // 修改时必须使用 `v.len`
 let slice2 = &v[0..v.len()];
 assert_eq!(slice1, slice2);
 // 切片是只读的
 // 注意:切片和 `&Vec` 是不同的类型,后者仅仅是 `Vec` 的引用,并可以通过解引用直接获取 `Vec`
 let vec_ref: &mut Vec<i32> = &mut v;
 (*vec_ref).push(4);
 let slice3 = &mut Vec::from(&v[0..3]);
 slice3.push(4);
 assert_eq!(slice3, &[1, 2, 3, 4]);
 println!("Success!")
}

第六题

// 修复错误
fn main() {
 let mut vec = Vec::with_capacity(10);
 assert_eq!(vec.len(), 0);
 assert_eq!(vec.capacity(), 10);
 // 由于提前设置了足够的容量,这里的循环不会造成任何内存分配...
 for i in 0..10 {
 vec.push(i);
 }
 assert_eq!(vec.len(), 10);
 assert_eq!(vec.capacity(), 10);
 // ...但是下面的代码会造成新的内存分配
 vec.push(11);
 assert_eq!(vec.len(), 11);
 assert!(vec.capacity() >= 11);
 // 填写一个合适的值,在 `for` 循环运行的过程中,不会造成任何内存分配
 let mut vec = Vec::with_capacity(101);
 for i in 0..100 {
 vec.push(i);
 }
 assert_eq!(vec.len(), 100);
 assert_eq!(vec.capacity(), 101);
 println!("Success!")
}

第七题

#[derive(Debug, PartialEq)]
enum IpAddr {
 V4(String),
 V6(String),
}
fn main() {
 // 填空
 let v : Vec<IpAddr>= vec![
 IpAddr::V4("127.0.0.1".to_string()),
 IpAddr::V6("::1".to_string()),
 ];
 // 枚举的比较需要派生 PartialEq 特征
 assert_eq!(v[0], IpAddr::V4("127.0.0.1".to_string()));
 assert_eq!(v[1], IpAddr::V6("::1".to_string()));
 println!("Success!")
}

第八题

trait IpAddr {
 fn display(&self);
}
struct V4(String);
impl IpAddr for V4 {
 fn display(&self) {
 println!("ipv4: {:?}",self.0)
 }
}
struct V6(String);
impl IpAddr for V6 {
 fn display(&self) {
 println!("ipv6: {:?}",self.0)
 }
}
fn main() {
 // 填空
 let v: Vec<Box<dyn IpAddr>>= vec![
 Box::new(V4("127.0.0.1".to_string())),
 Box::new(V6("::1".to_string())),
 ];
 for ip in v {
 ip.display();
 }
}

collections/vector #214

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giscus[bot] bot Apr 16, 2022

collections/vector

Replies: 23 comments · 5 replies

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