add solutions for string.md

This commit is contained in:
sunface
2022-03-02 20:57:13 +08:00
parent 2d7e251e8b
commit 0f4685dcf0
6 changed files with 355 additions and 34 deletions

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@@ -3,7 +3,7 @@ The type of string literal `"hello, world"` is `&str`, e.g `let s: &str = "hello
### str and &str
🌟 We can't use `str` type in normal ways, but we can use `&str`
1. 🌟 We can't use `str` type in normal ways, but we can use `&str`
```rust,editable
@@ -14,7 +14,7 @@ fn main() {
```
🌟🌟🌟 We can only use `str` by boxed it, `&` can be used to convert `Box<str>` to `&str`
2. 🌟🌟 We can only use `str` by boxed it, `&` can be used to convert `Box<str>` to `&str`
```rust,editable
@@ -32,7 +32,7 @@ fn greetings(s: &str) {
### String
`String` type is defined in std and stored as a vector of bytes (Vec<u8>), but guaranteed to always be a valid UTF-8 sequence. String is heap allocated, growable and not null terminated.
🌟
3. 🌟
```rust,editable
// fill the blank
@@ -45,13 +45,13 @@ fn main() {
}
```
🌟🌟🌟
4. 🌟🌟🌟
```rust,editable
// fix all errors without adding newline
fn main() {
let s = String::from("hello");
s.push(',');`
s.push(',');
s.push(" world");
s += "!".to_string();
@@ -59,7 +59,7 @@ fn main() {
}
```
🌟🌟 `replace` can be used to replace substring
5. 🌟🌟 `replace` can be used to replace substring
```rust,editable
// fill the blank
@@ -74,11 +74,11 @@ fn main() {
More `String` methods can be found under [String](https://doc.rust-lang.org/std/string/struct.String.html) module.
🌟🌟 You can only concat a `String` with `&str`, and `String`'s ownership can be moved to another variable
6. 🌟🌟 You can only concat a `String` with `&str`, and `String`'s ownership can be moved to another variable
```rust,editable
// fix errors
// fix errors without removing any line
fn main() {
let s1 = String::from("hello,");
let s2 = String::from("world!");
@@ -91,7 +91,7 @@ fn main() {
### &str and String
Opsite to the seldom using of `str`, `&str` and `String` are used everywhere!
🌟🌟 `&str` can be converted to `String` in two ways
7. 🌟🌟 `&str` can be converted to `String` in two ways
```rust,editable
// fix error with at lest two solutions
@@ -105,7 +105,7 @@ fn greetings(s: String) {
}
```
🌟🌟 We can use `String::from` or `to_string` to convert a `&str` to `String`
8. 🌟🌟 We can use `String::from` or `to_string` to convert a `&str` to `String`
```rust,editable
@@ -117,7 +117,7 @@ fn main() {
```
### string escapes
🌟
9. 🌟
```rust,editable
fn main() {
// You can use escapes to write bytes by their hexadecimal values
@@ -140,7 +140,7 @@ fn main() {
}
```
🌟🌟🌟 Sometimes there are just too many characters that need to be escaped or it's just much more convenient to write a string out as-is. This is where raw string literals come into play.
10. 🌟🌟🌟 Sometimes there are just too many characters that need to be escaped or it's just much more convenient to write a string out as-is. This is where raw string literals come into play.
```rust,editable
@@ -211,7 +211,7 @@ fn main() {
A more detailed listing of the ways to write string literals and escape characters is given in the ['Tokens' chapter](https://doc.rust-lang.org/reference/tokens.html) of the Rust Reference.
### string index
🌟🌟 You can't use index to access a char in a string, but you can use slice `&s1[start..end]`.
11. 🌟🌟🌟 You can't use index to access a char in a string, but you can use slice `&s1[start..end]`.
```rust,editable
@@ -226,7 +226,7 @@ fn main() {
```
### operate on UTF8 string
🌟
12. 🌟
```rust,editable
fn main() {

View File

@@ -1,7 +1,7 @@
# Reference and Borrowing
### Reference
🌟
1. 🌟
```rust,editable
fn main() {
@@ -9,11 +9,11 @@ fn main() {
// fill the blank
let p = __;
println!("the memory address of x is {:p}", p); // output: 0x16fa3ac84
println!("the memory address of x is {:p}", p); // one possible output: 0x16fa3ac84
}
```
🌟
2. 🌟
```rust,editable
fn main() {
@@ -25,7 +25,7 @@ fn main() {
}
```
🌟
3. 🌟
```rust,editable
// fix error
@@ -38,20 +38,22 @@ fn main() {
fn borrow_object(s: &String) {}
```
🌟
4. 🌟
```rust,editable
// fix error
fn main() {
let mut s = String::from("hello, ");
borrow_object(&s)
push_str(s)
}
fn borrow_object(s: &mut String) {}
fn push_str(s: &mut String) {
s.push_str("world")
}
```
🌟🌟
5. 🌟🌟
```rust,editable
fn main() {
@@ -67,7 +69,7 @@ fn main() {
#### ref
`ref` can be used to take references to a value, similar to `&`.
🌟🌟🌟
6. 🌟🌟🌟
```rust,editable
fn main() {
@@ -90,7 +92,7 @@ fn get_addr(r: &char) -> String {
```
### Borrowing rules
🌟
7. 🌟
```rust,editable
// remove something to make it work
@@ -106,7 +108,7 @@ fn main() {
```
#### Mutablity
🌟 Error: Borrow a immutable object as mutable
8. 🌟 Error: Borrow a immutable object as mutable
```rust,editable
fn main() {
@@ -119,7 +121,7 @@ fn main() {
fn borrow_object(s: &mut String) {}
```
🌟🌟 Ok: Borrow a mutable object as immutable
9. 🌟🌟 Ok: Borrow a mutable object as immutable
```rust,editable
// this code has no errors!
@@ -135,7 +137,7 @@ fn borrow_object(s: &String) {}
```
### NLL
🌟🌟
10. 🌟🌟
```rust,editable
// comment one line to make it work
@@ -151,7 +153,7 @@ fn main() {
}
```
🌟🌟🌟
11. 🌟🌟
```rust,editable
fn main() {