41. Reverse a string
反转字符串
package main
import "fmt"
func Reverse(s string) string {
runes := []rune(s)
for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
runes[i], runes[j] = runes[j], runes[i]
}
return string(runes)
}
func main() {
input := "The quick brown 狐 jumped over the lazy 犬"
fmt.Println(Reverse(input))
// Original string unaltered
fmt.Println(input)
}
输出
犬 yzal eht revo depmuj 狐 nworb kciuq ehT
The quick brown 狐 jumped over the lazy 犬
let t = s.chars().rev().collect::<String>();
or
fn main() {
let s = "lorém ipsüm dolör sit amor ❤ ";
let t: String = s.chars().rev().collect();
println!("{}", t);
}
输出
❤ roma tis rölod müspi mérol
42. Continue outer loop
Print each item v of list a which in not contained in list b. For this, write an outer loop to iterate on a and an inner loop to iterate on b.
打印列表a中不包含在列表b中的每个项目v。 为此，编写一个外部循环来迭代a，编写一个内部循环来迭代b。
package main
import "fmt"
func printSubtraction(a []int, b []int) {
mainloop:
for _, v := range a {
for _, w := range b {
if v == w {
continue mainloop
}
}
fmt.Println(v)
}
}
func main() {
a := []int{1, 2, 3, 4}
b := []int{2, 4, 6, 8}
printSubtraction(a, b)
}
mainloop is a label used to refer to the outer loop.
输出
1
3
fn main() {
let a = ['a', 'b', 'c', 'd', 'e'];
let b = [ 'b', 'd' ];
'outer: for va in &a {
for vb in &b {
if va == vb {
continue 'outer;
}
}
println!("{}", va);
}
}
'outer is a label used to refer to the outer loop. Labels in Rust start with a '.
输出
a
c
e
43. Break outer loop
Look for a negative value v in 2D integer matrix m. Print it and stop searching.
在2D整数矩阵m中寻找一个负值v，打印出来，停止搜索。
package main
import "fmt"
import "os"
var m = [][]int{
{1, 2, 3},
{11, 0, 30},
{5, -20, 55},
{0, 0, -60},
}
func main() {
mainloop:
for i, line := range m {
fmt.Fprintln(os.Stderr, "Searching in line", i)
for _, v := range line {
if v < 0 {
fmt.Println("Found ", v)
break mainloop
}
}
}
fmt.Println("Done.")
}
mainloop is a label used to refer to the outer loop.
输出
Searching in line 0
Searching in line 1
Searching in line 2
Found -20
Done.
fn main() {
let m = vec![
vec![1, 2, 3],
vec![11, 0, 30],
vec![5, -20, 55],
vec![0, 0, -60],
];
'outer: for v in m {
'inner: for i in v {
if i < 0 {
println!("Found {}", i);
break 'outer;
}
}
}
}
Loop label syntax is similar to lifetimes.
输出
Found -20
44. Insert element in list
Insert element x at position i in list s. Further elements must be shifted to the right.
在列表s的位置I插入元素x。其他元素必须向右移动。
package main
import "fmt"
func main() {
s := make([]int, 2)
s[0] = 0
s[1] = 2
fmt.Println(s)
// insert one at index one
s = append(s, 0)
copy(s[2:], s[1:])
s[1] = 1
fmt.Println(s)
}
输出
[0 2]
[0 1 2]
fn main() {
let mut vec = vec![1, 2, 3];
vec.insert(1, 4);
assert_eq!(vec, [1, 4, 2, 3]);
vec.insert(4, 5);
assert_eq!(vec, [1, 4, 2, 3, 5]);
}
45. Pause execution for 5 seconds
在继续下一个指令之前，在当前线程中休眠5秒钟。
package main
import (
"fmt"
"time"
)
func main() {
time.Sleep(5 * time.Second)
fmt.Println("Done.")
}
use std::{thread, time};
thread::sleep(time::Duration::from_secs(5));
46. Extract beginning of string (prefix)
Create string t consisting of the 5 first characters of string s. Make sure that multibyte characters are properly handled.
创建由字符串s的前5个字符组成的字符串t。 确保正确处理多字节字符。
package main
import "fmt"
func main() {
s := "Привет"
t := string([]rune(s)[:5])
fmt.Println(t)
}
输出
Приве
fn main() {
let s = "été 😁 torride";
let t = s.char_indices().nth(5).map_or(s, |(i, _)| &s[..i]);
println!("{}", t);
}
输出
été 😁
47. Extract string suffix
Create string t consisting in the 5 last characters of string s. Make sure that multibyte characters are properly handled.
创建由字符串s的最后5个字符组成的字符串t。 确保正确处理多字节字符
package main
import "fmt"
func main() {
s := "hello, world! 문자"
t := string([]rune(s)[len([]rune(s))-5:])
fmt.Println(t)
}
输出
d! 문자
fn main() {
let s = "tükörfúrógép";
let last5ch = s.chars().count() - 5;
let s2: String = s.chars().skip(last5ch).collect();
println!("{}", s2);
}
输出
rógép
48. Multi-line string literal
Assign to variable s a string literal consisting in several lines of text, including newlines.
给变量s赋值一个由几行文本组成的字符串，包括换行符。
package main
import (
"fmt"
)
func main() {
s := `Huey
Dewey
Louie`
fmt.Println(s)
}
输出
Huey
Dewey
Louie
fn main() {
let s = "line 1
line 2
line 3";
print!("{}", &s);
}
输出
line 1
line 2
line 3
or
fn main() {
let s = r#"Huey
Dewey
Louie"#;
print!("{}", &s);
}
输出
Huey
Dewey
Louie
49. Split a space-separated string
拆分用空格分隔的字符串
Build list chunks consisting in substrings of input string s, separated by one or more space characters.
构建由输入字符串的子字符串组成的列表块，由一个或多个空格字符分隔。
package main
import (
"fmt"
"strings"
)
func main() {
s := "Un dos tres"
chunks := strings.Split(s, " ")
fmt.Println(len(chunks))
fmt.Println(chunks)
s = " Un dos tres "
chunks = strings.Split(s, " ")
fmt.Println(len(chunks))
fmt.Println(chunks)
s = "Un dos"
chunks = strings.Split(s, " ")
fmt.Println(len(chunks))
fmt.Println(chunks)
}
输出
3
[Un dos tres]
5
[ Un dos tres ]
3
[Un dos]
or
package main
import (
"fmt"
"strings"
)
func main() {
s := "hello world"
chunks := strings.Fields(s)
fmt.Println(chunks)
}
输出为
[hello world]
and
package main
import (
"fmt"
"strings"
)
func main() {
s := "Un dos tres"
chunks := strings.Fields(s)
fmt.Println(len(chunks))
fmt.Println(chunks)
s = " Un dos tres "
chunks = strings.Fields(s)
fmt.Println(len(chunks))
fmt.Println(chunks)
s = "Un dos"
chunks = strings.Fields(s)
fmt.Println(len(chunks))
fmt.Println(chunks)
}
输出
3
[Un dos tres]
3
[Un dos tres]
2
[Un dos]
strings.Fields 就只能干这个事儿
fn main() {
let s = "What a mess";
let chunks: Vec<_> = s.split_whitespace().collect();
println!("{:?}", chunks);
}
输出
["What", "a", "mess"]
or
fn main() {
let s = "What a mess";
let chunks: Vec<_> = s.split_ascii_whitespace().collect();
println!("{:?}", chunks);
}
输出
["What", "a", "mess"]
or
fn main() {
let s = "What a mess";
let chunks: Vec<_> = s.split(' ').collect();
println!("{:?}", chunks);
}
输出
["What", "a", "", "mess"]
50. Make an infinite loop
写一个无限循环
for {
// Do something
}
package main
import "fmt"
func main() {
k := 0
for {
fmt.Println("Hello, playground")
k++
if k == 5 {
break
}
}
}
输出
Hello, playground
Hello, playground
Hello, playground
Hello, playground
Hello, playground
loop {
// Do something
}
51. Check if map contains key
Determine whether map m contains an entry for key k
检查map是否有某个key
package main
import (
"fmt"
)
func main() {
m := map[string]int{
"uno": 1,
"dos": 2,
"tres": 3,
}
k := "cinco"
_, ok := m[k]
fmt.Printf("m contains key %q: %v\n", k, ok)
k = "tres"
_, ok = m[k]
fmt.Printf("m contains key %q: %v\n", k, ok)
}
输出
m contains key "cinco": false
m contains key "tres": true
use std::collections::HashMap;
fn main() {
let mut m = HashMap::new();
m.insert(1, "a");
m.insert(2, "b");
let k = 2;
let hit = m.contains_key(&k);
println!("{:?}", hit);
}
52. Check if map contains value
检查map中是否有某个值
package main
import (
"fmt"
)
func containsValue(m map[K]T, v T) bool {
for _, x := range m {
if x == v {
return true
}
}
return false
}
// Arbitrary types for K, T.
type K string
type T int
func main() {
m := map[K]T{
"uno": 1,
"dos": 2,
"tres": 3,
}
var v T = 5
ok := containsValue(m, v)
fmt.Printf("m contains value %d: %v\n", v, ok)
v = 3
ok = containsValue(m, v)
fmt.Printf("m contains value %d: %v\n", v, ok)
}
输出
m contains value 5: false
m contains value 3: true
use std::collections::BTreeMap;
fn main() {
let mut m = BTreeMap::new();
m.insert(11, "one");
m.insert(22, "twenty-two");
{
let v = "eight";
let does_contain = m.values().any(|&val| *val == *v);
println!("{:?}", does_contain);
}
{
let v = "twenty-two";
let does_contain = m.values().any(|&val| *val == *v);
println!("{:?}", does_contain);
}
}
53. Join a list of strings
字符串连接
package main
import (
"fmt"
"strings"
)
func main() {
x := []string{"xxx", "bbb", "aaa"}
y := strings.Join(x, "&")
fmt.Println(y)
}
输出
xxx&bbb&aaa
fn main() {
let x = vec!["Lorem", "ipsum", "dolor", "sit", "amet"];
let y = x.join(", ");
println!("{}", y);
}
输出
Lorem, ipsum, dolor, sit, amet
54. Compute sum of integers
计算整数之和
package main
import "fmt"
func main() {
x := []int{1, 2, 3}
s := 0
for _, v := range x {
s += v
}
fmt.Println(s)
}
输出
6
fn main() {
let x: Vec<usize> = (0..=10_000).collect();
eprintln!("Sum of 0-10,000 = {}", x.iter().sum::<usize>())
}
输出
Sum of 0-10,000 = 50005000
55. Convert integer to string
将整数转换为字符串
package main
import (
"fmt"
"strconv"
)
func main() {
var i int = 1234
s := strconv.Itoa(i)
fmt.Println(s)
}
输出
1234
or
package main
import (
"fmt"
"strconv"
)
func main() {
var i int64 = 1234
s := strconv.FormatInt(i, 10)
fmt.Println(s)
}
输出
1234
or
package main
import "fmt"
import "math/big"
func main() {
var i int = 1234
s := fmt.Sprintf("%d", i)
fmt.Println(s)
var j int = 5678
s = fmt.Sprintf("%d", j)
fmt.Println(s)
var k *big.Int = big.NewInt(90123456)
s = fmt.Sprintf("%d", k)
fmt.Println(s)
}
输出
1234
5678
90123456
fn main() {
let i = 123;
let s = i.to_string();
println!("{}", s);
}
输出
123
or
fn main() {
let i = 123;
let s = format!("{}", i);
println!("{}", s);
}
输出
123
56. Launch 1000 parallel tasks and wait for completion
Fork-join : launch the concurrent execution of procedure f with parameter i from 1 to 1000. Tasks are independent and f(i) doesn't return any value. Tasks need not run all at the same time, so you may use a pool. Wait for the completion of the 1000 tasks and then print "Finished".
创建1000个并行任务，并等待其完成
package main
import (
"fmt"
"math/rand"
"sync"
"time"
)
func f(i int) {
d := rand.Int() % 10000
time.Sleep(time.Duration(d))
fmt.Printf("Hello %v\n", i)
}
func main() {
var wg sync.WaitGroup
wg.Add(1000)
for i := 1; i <= 1000; i++ {
go func(i int) {
f(i)
wg.Done()
}(i)
}
wg.Wait()
fmt.Println("Finished")
}
输出
Hello 741
Hello 651
Hello 49
...（共计1000个）
Hello xxx
use std::thread;
fn f(i: i32) {
i + 1;
}
fn main() {
let threads: Vec<_> = (0..10).map(|i| thread::spawn(move || f(i))).collect();
for t in threads {
t.join();
}
}
57. Filter list
Create list y containing items from list x satisfying predicate p. Respect original ordering. Don't modify x in-place.
过滤list中的值
package main
import "fmt"
type T int
func main() {
x := []T{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
p := func(t T) bool { return t%2 == 0 }
y := make([]T, 0, len(x))
for _, v := range x {
if p(v) {
y = append(y, v)
}
}
fmt.Println(y)
}
or
package main
import "fmt"
type T int
func main() {
x := []T{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
p := func(t T) bool { return t%2 == 0 }
n := 0
for _, v := range x {
if p(v) {
n++
}
}
y := make([]T, 0, n)
for _, v := range x {
if p(v) {
y = append(y, v)
}
}
fmt.Println(y)
}
输出
[2 4 6 8 10]
fn main() {
let x = vec![1, 2, 3, 4, 5, 6];
let y: Vec<_> = x.iter()
.filter(|&x| x % 2 == 0)
.collect();
println!("{:?}", y);
}
输出
[2, 4, 6]
58. Extract file content to a string
提取字符串的文件内容
package main
import "fmt"
import "io/ioutil"
func main() {
f := "data.txt"
b, err := ioutil.ReadFile(f)
if err != nil {
panic(err)
}
lines := string(b)
fmt.Println(lines)
}
// Create file in fake FS of the Playground. init is executed before main.
func init() {
err := ioutil.WriteFile("data.txt", []byte(`Un
Dos
Tres`), 0644)
if err != nil {
panic(err)
}
}
输出
Un
Dos
Tres
use std::fs::File;
use std::io::prelude::*;
fn main() -> Result<(), ()> {
let f = "Cargo.toml";
let mut file = File::open(f).expect("Can't open file.");
let mut lines = String::new();
file.read_to_string(&mut lines)
.expect("Can't read file contents.");
println!("{}", lines);
Ok(())
}
or
use std::fs;
fn main() {
let f = "Cargo.toml";
let lines = fs::read_to_string(f).expect("Can't read file.");
println!("{}", lines);
}
59. Write to standard error stream
Print the message "x is negative" to standard error (stderr), with integer x value substitution (e.g. "-2 is negative").
写入标准错误流
package main
import (
"fmt"
"os"
)
func main() {
x := -2
fmt.Fprintln(os.Stderr, x, "is negative")
}
输出
-2 is negative
fn main() {
let x = -3;
eprintln!("{} is negative", x);
}
输出
-3 is negative
60. Read command line argument
读取命令行参数
import "os"
x := os.Args[1]
use std::env;
fn main() {
let first_arg = env::args().skip(1).next();
let fallback = "".to_owned();
let x = first_arg.unwrap_or(fallback);
println!("{:?}", x);
}
输出
""
