collections/vector #214

// 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 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 · 2023-01-06T03:25:37Z

Bruce012356
Jan 6, 2023 — with giscus

mark

0 replies

Nixicodo · 2023-03-02T08:13:37Z

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 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 · 2023-05-03T15:59:27Z

XU0618
May 3, 2023 — with giscus

lala

0 replies

Ghy0202 · 2023-07-18T09:17:29Z

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 · 2023-08-06T12:57:03Z

chenhai998
Aug 6, 2023 — with giscus

done

0 replies

yuliang0225 · 2023-12-24T08:45:04Z

yuliang0225
Dec 24, 2023 — with giscus

7好阴哦

0 replies

CynicalHeart · 2023-12-24T11:11:19Z

CynicalHeart
Dec 24, 2023 — with giscus

到这期确实变难了不少。

0 replies

pypanta · 2024-01-19T08:18:42Z

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 · 2024-02-22T07:09:09Z

BokutoMan
Feb 22, 2024 — with giscus

down

0 replies

felipe300 · 2024-02-29T00:52:13Z

felipe300
Feb 29, 2024 — with giscus

done

0 replies

ldd19920711 · 2024-03-03T15:28:58Z

ldd19920711
Mar 3, 2024 — with giscus

mark 11.2 5

0 replies

DylanJinx · 2024-05-10T08:19:48Z

DylanJinx
May 10, 2024 — with giscus

done~~~

0 replies

TDAkory · 2024-07-20T09:35:30Z

TDAkory
Jul 20, 2024 — with giscus

mark finished

0 replies

DataShare-duo · 2024-09-26T06:34:20Z

DataShare-duo
Sep 26, 2024 — with giscus

难起来了

0 replies

bansal-harsh-2504 · 2024-12-18T12:56:53Z

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

Day 9
Done✅

0 replies

gastrodia · 2025-01-10T10:39:47Z

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();
    }
}

0 replies

FlandreLiao · 2025-01-13T13:42:30Z

FlandreLiao
Jan 13, 2025 — with giscus

done

0 replies

meifu2027 · 2025-03-24T14:41:05Z

meifu2027
Mar 24, 2025 — with giscus

done

0 replies

collections/vector #214

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