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452 lines
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<main>
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<h1 id="vector"><a class="header" href="#vector">Vector</a></h1>
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<p>Vectors are resizable arrays. Like slices, their size is not known at compile time, but they can grow or shrink at any time.</p>
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<h3 id="basic-operations"><a class="header" href="#basic-operations">Basic Operations</a></h3>
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<ol>
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<li>🌟🌟🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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fn main() {
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let arr: [u8; 3] = [1, 2, 3];
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let v = Vec::from(arr);
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is_vec(&v);
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let v = vec![1, 2, 3];
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is_vec(&v);
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// vec!(..) and vec![..] are same macros, so
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let v = vec!(1, 2, 3);
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is_vec(&v);
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// In code below, v is Vec<[u8; 3]> , not Vec<u8>
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// USE Vec::new and `for` to rewrite the below code
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let v1 = vec!(arr);
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is_vec(&v1);
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assert_eq!(v, v1);
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println!("Success!");
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}
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fn is_vec(v: &Vec<u8>) {}</code></pre></pre>
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<ol start="2">
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<li>🌟🌟 A Vec can be extended with <code>extend</code> method</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// FILL in the blank
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fn main() {
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let mut v1 = Vec::from([1, 2, 4]);
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v1.pop();
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v1.push(3);
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let mut v2 = Vec::new();
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v2.__;
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assert_eq!(v1, v2);
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println!("Success!");
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}</code></pre></pre>
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<h3 id="turn-x-into-vec"><a class="header" href="#turn-x-into-vec">Turn X Into Vec</a></h3>
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<ol start="3">
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<li>🌟🌟🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// FILL in the blanks
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fn main() {
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// Array -> Vec
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// impl From<[T; N]> for Vec
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let arr = [1, 2, 3];
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let v1 = __(arr);
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let v2: Vec<i32> = arr.__();
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assert_eq!(v1, v2);
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// String -> Vec
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// impl From<String> for Vec
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let s = "hello".to_string();
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let v1: Vec<u8> = s.__();
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let s = "hello".to_string();
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let v2 = s.into_bytes();
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assert_eq!(v1, v2);
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// impl<'_> From<&'_ str> for Vec
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let s = "hello";
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let v3 = Vec::__(s);
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assert_eq!(v2, v3);
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// Iterators can be collected into vectors
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let v4: Vec<i32> = [0; 10].into_iter().collect();
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assert_eq!(v4, vec![0; 10]);
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println!("Success!");
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}</code></pre></pre>
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<h3 id="indexing"><a class="header" href="#indexing">Indexing</a></h3>
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<ol start="4">
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<li>🌟🌟🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// FIX the error and IMPLEMENT the code
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fn main() {
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let mut v = Vec::from([1, 2, 3]);
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for i in 0..5 {
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println!("{:?}", v[i])
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}
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for i in 0..5 {
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// IMPLEMENT the code here...
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}
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assert_eq!(v, vec![2, 3, 4, 5, 6]);
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println!("Success!");
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}</code></pre></pre>
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<h3 id="slicing"><a class="header" href="#slicing">Slicing</a></h3>
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<p>Immutable or mutable slices of Vecs can be taken, using <code>&</code> or <code>&mut</code>, respectively.</p>
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<p>In Rust, it’s more common to pass immutable slices as arguments rather than vectors when you just want to provide read access, as this is more flexible (no move) and efficient (no copy). The same goes for <code>String</code> and <code>&str</code>.</p>
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<ol start="5">
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<li>🌟🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">
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// FIX the errors
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fn main() {
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let mut v = vec![1, 2, 3];
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let slice1 = &v[..];
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// Out of bounds will cause a panic
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// You must use `v.len` here
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let slice2 = &v[0..4];
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assert_eq!(slice1, slice2);
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// A slice can also be mutable, in which
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// case mutating it will mutate its underlying Vec.
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// Note: slice and &Vec are different
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let vec_ref: &mut Vec<i32> = &mut v;
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(*vec_ref).push(4);
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let slice3 = &mut v[0..3];
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slice3[3] = 42;
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assert_eq!(slice3, &[1, 2, 3, 42]);
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assert_eq!(v, &[1, 2, 3, 42]);
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println!("Success!");
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}</code></pre></pre>
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<h3 id="capacity"><a class="header" href="#capacity">Capacity</a></h3>
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<p>The capacity of a vector is the amount of space allocated for any future elements that will be added onto the vector. This is not to be confused with the length of a vector, which specifies the number of actual elements within the vector. If a vector’s length exceeds its capacity, its capacity will automatically be increased, but its elements will have to be reallocated.</p>
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<p>For example, a vector with capacity 10 and length 0 would be an empty vector with space for 10 more elements. Pushing 10 or fewer elements onto the vector will not change its capacity or cause reallocation to occur. However, if the vector’s length is increased to 11, it will have to reallocate, which can be slow. For this reason, it is recommended to use <code>Vec::with_capacity </code>whenever possible to specify how big the vector is expected to get.</p>
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<ol start="6">
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<li>🌟🌟</li>
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</ol>
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<pre><pre class="playground"><code class="language-rust editable edition2021">// FIX the errors
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fn main() {
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let mut vec = Vec::with_capacity(10);
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// The vector contains no items, even though it has capacity for more
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assert_eq!(vec.len(), __);
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assert_eq!(vec.capacity(), 10);
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// These are all done without reallocating...
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for i in 0..10 {
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vec.push(i);
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}
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assert_eq!(vec.len(), __);
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assert_eq!(vec.capacity(), __);
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// ...but this may make the vector reallocate
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vec.push(11);
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assert_eq!(vec.len(), 11);
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assert!(vec.capacity() >= 11);
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// Fill in an appropriate value to make the `for` done without reallocating
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let mut vec = Vec::with_capacity(__);
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for i in 0..100 {
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vec.push(i);
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}
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assert_eq!(vec.len(), __);
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assert_eq!(vec.capacity(), __);
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println!("Success!");
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}</code></pre></pre>
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<h3 id="store-distinct-types-in-vector"><a class="header" href="#store-distinct-types-in-vector">Store distinct types in Vector</a></h3>
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<p>The elements in a vector must be the same type, for example , the code below will cause an error:</p>
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<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
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let v = vec![1, 2.0, 3];
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}</code></pre></pre>
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<p>But we can use enums or trait objects to store distinct types.</p>
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<ol start="7">
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||
<li>🌟🌟</li>
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||
</ol>
|
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<pre><pre class="playground"><code class="language-rust editable edition2021">#[derive(Debug)]
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enum IpAddr {
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V4(String),
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V6(String),
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}
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fn main() {
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// FILL in the blank
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let v : Vec<IpAddr>= __;
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|
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// Comparing two enums need to derive the PartialEq trait
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assert_eq!(v[0], IpAddr::V4("127.0.0.1".to_string()));
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||
assert_eq!(v[1], IpAddr::V6("::1".to_string()));
|
||
|
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println!("Success!");
|
||
}</code></pre></pre>
|
||
<ol start="8">
|
||
<li>🌟🌟</li>
|
||
</ol>
|
||
<pre><pre class="playground"><code class="language-rust editable edition2021">trait IpAddr {
|
||
fn display(&self);
|
||
}
|
||
|
||
struct V4(String);
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||
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() {
|
||
// FILL in the blank
|
||
let v: __= vec![
|
||
Box::new(V4("127.0.0.1".to_string())),
|
||
Box::new(V6("::1".to_string())),
|
||
];
|
||
|
||
for ip in v {
|
||
ip.display();
|
||
}
|
||
}</code></pre></pre>
|
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