題圖來自 Go vs. Rust performance comparison: The basics

61. Get current date

獲取當(dāng)前時(shí)間

package?main

import?(
?"fmt"
?"time"
)

func?main()?{
?d?:=?time.Now()
?fmt.Println("Now?is",?d)
?//?The?Playground?has?a?special?sandbox,?so?you?may?get?a?Time?value?fixed?in?the?past.
}

Now is 2009-11-10 23:00:00 +0000 UTC m=+0.000000001

extern?crate?time;
let?d?=?time::now();

or

use?std::time::SystemTime;

fn?main()?{
????let?d?=?SystemTime::now();
????println!("{:?}",?d);
}

SystemTime { tv_sec: 1526318418, tv_nsec: 699329521 }

62. Find substring position

字符串查找

查找子字符串位置

package?main

import?(
?"fmt"
?"strings"
)

func?main()?{
?x?:=?"été?chaud"

?{
??y?:=?"chaud"
??i?:=?strings.Index(x,?y)
??fmt.Println(i)
?}

?{
??y?:=?"froid"
??i?:=?strings.Index(x,?y)
??fmt.Println(i)
?}
}

i is the byte index of y in x, not the character (rune) index. i will be -1 if y is not found in x.

6
-1

fn?main()?{
????let?x?=?"été?chaud";
????
????let?y?=?"chaud";
????let?i?=?x.find(y);
????println!("{:?}",?i);
????
????let?y?=?"froid";
????let?i?=?x.find(y);
????println!("{:?}",?i);
}

Some(6)
None

63. Replace fragment of a string

替換字符串片段

package?main

import?(
?"fmt"
?"strings"
)

func?main()?{
?x?:=?"oink?oink?oink"
?y?:=?"oink"
?z?:=?"moo"
?x2?:=?strings.Replace(x,?y,?z,?-1)
?fmt.Println(x2)
}

moo moo moo

fn?main()?{
????let?x?=?"lorem?ipsum?dolor?lorem?ipsum";
????let?y?=?"lorem";
????let?z?=?"LOREM";

????let?x2?=?x.replace(&y,?&z);
????
????println!("{}",?x2);
}

LOREM ipsum dolor LOREM ipsum

64. Big integer : value 3 power 247

超大整數(shù)

package?main

import?"fmt"
import?"math/big"

func?main()?{
?x?:=?new(big.Int)
?x.Exp(big.NewInt(3),?big.NewInt(247),?nil)
?fmt.Println(x)
}

7062361041362837614435796717454722507454089864783271756927542774477268334591598635421519542453366332460075473278915787

extern?crate?num;
use?num::bigint::ToBigInt;

fn?main()?{
????let?a?=?3.to_bigint().unwrap();
????let?x?=?num::pow(a,?247);
????println!("{}",?x)
}

7062361041362837614435796717454722507454089864783271756927542774477268334591598635421519542453366332460075473278915787

65. Format decimal number

格式化十進(jìn)制數(shù)

package?main

import?"fmt"

func?main()?{
?x?:=?0.15625
?s?:=?fmt.Sprintf("%.1f%%",?100.0*x)
?fmt.Println(s)
}

15.6%

fn?main()?{
????let?x?=?0.15625f64;
????let?s?=?format!("{:.1}%",?100.0?*?x);
????
????println!("{}",?s);
}

15.6%

66. Big integer exponentiation

大整數(shù)冪運(yùn)算

package?main

import?"fmt"
import?"math/big"

func?exp(x?*big.Int,?n?int)?*big.Int?{
?nb?:=?big.NewInt(int64(n))
?var?z?big.Int
?z.Exp(x,?nb,?nil)
?return?&z
}

func?main()?{
?x?:=?big.NewInt(3)
?n?:=?5
?z?:=?exp(x,?n)
?fmt.Println(z)
}

243

extern?crate?num;

use?num::bigint::BigInt;

fn?main()?{
????let?x?=?BigInt::parse_bytes(b"600000000000",?10).unwrap();
????let?n?=?42%

67. Binomial coefficient "n choose k"

Calculate binom(n, k) = n! / (k! * (n-k)!). Use an integer type able to handle huge numbers.

二項(xiàng)式系數(shù)“n選擇k”

package?main

import?(
?"fmt"
?"math/big"
)

func?main()?{
?z?:=?new(big.Int)
?
?z.Binomial(4,?2)
?fmt.Println(z)
?
?z.Binomial(133,?71)
?fmt.Println(z)
}

6
555687036928510235891585199545206017600

extern?crate?num;

use?num::bigint::BigInt;
use?num::bigint::ToBigInt;
use?num::traits::One;

fn?binom(n:?u64,?k:?u64)?->?BigInt?{
????let?mut?res?=?BigInt::one();
????for?i?in?0..k?{
????????res?=?(res?*?(n?-?i).to_bigint().unwrap())?/
??????????????(i?+?1).to_bigint().unwrap();
????}
????res
}

fn?main()?{
????let?n?=?133;
????let?k?=?71;

????println!("{}",?binom(n,?k));
}

555687036928510235891585199545206017600

68. Create a bitset

創(chuàng)建位集合

package?main

import?(
?"fmt"
?"math/big"
)

func?main()?{
?var?x?*big.Int?=?new(big.Int)

?x.SetBit(x,?42,?1)

?for?_,?y?:=?range?[]int{13,?42}?{
??fmt.Println("x?has?bit",?y,?"set?to",?x.Bit(y))
?}
}

x?has?bit?13?set?to?0
x?has?bit?42?set?to?1

or

package?main

import?(
?"fmt"
)

const?n?=?1024

func?main()?{
?x?:=?make([]bool,?n)

?x[42]?=?true

?for?_,?y?:=?range?[]int{13,?42}?{
??fmt.Println("x?has?bit",?y,?"set?to",?x[y])
?}
}

x?has?bit?13?set?to?false
x?has?bit?42?set?to?true

or

package?main

import?(
?"fmt"
)

func?main()?{
?const?n?=?1024

?x?:=?NewBitset(n)

?x.SetBit(13)
?x.SetBit(42)
?x.ClearBit(13)

?for?_,?y?:=?range?[]int{13,?42}?{
??fmt.Println("x?has?bit",?y,?"set?to",?x.GetBit(y))
?}
}

type?Bitset?[]uint64

func?NewBitset(n?int)?Bitset?{
?return?make(Bitset,?(n+63)/64)
}

func?(b?Bitset)?GetBit(index?int)?bool?{
?pos?:=?index?/?64
?j?:=?index?%?64
?return?(b[pos]?&?(uint64(1)?<<?j))?!=?0
}

func?(b?Bitset)?SetBit(index?int)?{
?pos?:=?index?/?64
?j?:=?index?%?64
?b[pos]?|=?(uint64(1)?<<?j)
}

func?(b?Bitset)?ClearBit(index?int)?{
?pos?:=?index?/?64
?j?:=?index?%?64
?b[pos]?^=?(uint64(1)?<<?j)
}

x?has?bit?13?set?to?false
x?has?bit?42?set?to?true

fn?main()?{
????let?n?=?20;

????let?mut?x?=?vec![false;?n];

????x[3]?=?true;
????println!("{:?}",?x);
}

[false, false, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false]

69. Seed random generator

Use seed s to initialize a random generator.

If s is constant, the generator output will be the same each time the program runs. If s is based on the current value of the system clock, the generator output will be different each time.

隨機(jī)種子生成器

package?main

import?(
?"fmt"
?"math/rand"
)

func?main()?{
?var?s?int64?=?42
?rand.Seed(s)
?fmt.Println(rand.Int())
}

3440579354231278675

or

package?main

import?(
?"fmt"
?"math/rand"
)

func?main()?{
?var?s?int64?=?42
?r?:=?rand.New(rand.NewSource(s))
?fmt.Println(r.Int())
}

3440579354231278675

use?rand::{Rng,?SeedableRng,?rngs::StdRng};

fn?main()?{
????let?s?=?32;
????let?mut?rng?=?StdRng::seed_from_u64(s);
????
????println!("{:?}",?rng.gen::<f32>());
}

0.35038823

70. Use clock as random generator seed

Get the current datetime and provide it as a seed to a random generator. The generator sequence will be different at each run.

使用時(shí)鐘作為隨機(jī)生成器的種子

package?main

import?(
?"fmt"
?"math/rand"
?"time"
)

func?main()?{
?rand.Seed(time.Now().UnixNano())
?//?Well,?the?playground?date?is?actually?fixed?in?the?past,?and?the
?//?output?is?cached.
?//?But?if?you?run?this?on?your?workstation,?the?output?will?vary.
?fmt.Println(rand.Intn(999))
}

524

or

package?main

import?(
?"fmt"
?"math/rand"
?"time"
)

func?main()?{
?r?:=?rand.New(rand.NewSource(time.Now().UnixNano()))
?//?Well,?the?playground?date?is?actually?fixed?in?the?past,?and?the
?//?output?is?cached.
?//?But?if?you?run?this?on?your?workstation,?the?output?will?vary.
?fmt.Println(r.Intn(999))
}

524

use?rand::{Rng,?SeedableRng,?rngs::StdRng};
use?std::time::SystemTime;

fn?main()?{
????let?d?=?SystemTime::now()
????????.duration_since(SystemTime::UNIX_EPOCH)
????????.expect("Duration?since?UNIX_EPOCH?failed");
????let?mut?rng?=?StdRng::seed_from_u64(d.as_secs());
????
????println!("{:?}",?rng.gen::<f32>());
}

0.7326781

71. Echo program implementation

Basic implementation of the Echo program: Print all arguments except the program name, separated by space, followed by newline.
The idiom demonstrates how to skip the first argument if necessary, concatenate arguments as strings, append newline and print it to stdout.

實(shí)現(xiàn) Echo 程序

package?main
import?"fmt"
import?"os"
import?"strings"
func?main()?{
????fmt.Println(strings.Join(os.Args[1:],?"?"))
}

use?std::env;

fn?main()?{
????println!("{}",?env::args().skip(1).collect::<Vec<_>>().join("?"));
}

or

use?itertools::Itertools;
println!("{}",?std::env::args().skip(1).format("?"));

74. Compute GCD

Compute the greatest common divisor x of big integers a and b. Use an integer type able to handle huge numbers.

計(jì)算大整數(shù)a和b的最大公約數(shù)x。使用能夠處理大數(shù)的整數(shù)類型。

package?main

import?"fmt"
import?"math/big"

func?main()?{
?a,?b,?x?:=?new(big.Int),?new(big.Int),?new(big.Int)
?a.SetString("6000000000000",?10)
?b.SetString("9000000000000",?10)
?x.GCD(nil,?nil,?a,?b)
?fmt.Println(x)
}

3000000000000

extern?crate?num;

use?num::Integer;
use?num::bigint::BigInt;

fn?main()?{
????let?a?=?BigInt::parse_bytes(b"6000000000000",?10).unwrap();
????let?b?=?BigInt::parse_bytes(b"9000000000000",?10).unwrap();
????
????let?x?=?a.gcd(&b);
?
????println!("{}",?x);
}

3000000000000

75. Compute LCM

計(jì)算大整數(shù)a和b的最小公倍數(shù)x。使用能夠處理大數(shù)的整數(shù)類型。

Compute the least common multiple x of big integers a and b. Use an integer type able to handle huge numbers.

package?main

import?"fmt"
import?"math/big"

func?main()?{
?a,?b,?gcd,?x?:=?new(big.Int),?new(big.Int),?new(big.Int),?new(big.Int)
?a.SetString("6000000000000",?10)
?b.SetString("9000000000000",?10)
?gcd.GCD(nil,?nil,?a,?b)
?x.Div(a,?gcd).Mul(x,?b)
?fmt.Println(x)
}

18000000000000

extern?crate?num;

use?num::bigint::BigInt;
use?num::Integer;

fn?main()?{
????let?a?=?BigInt::parse_bytes(b"6000000000000",?10).unwrap();
????let?b?=?BigInt::parse_bytes(b"9000000000000",?10).unwrap();
????let?x?=?a.lcm(&b);
????println!("x?=?{}",?x);
}

x = 18000000000000

76. Binary digits from an integer

Create the string s of integer x written in base 2.
E.g. 13 -> "1101"

將十進(jìn)制整數(shù)轉(zhuǎn)換為二進(jìn)制數(shù)字

package?main

import?"fmt"
import?"strconv"

func?main()?{
?x?:=?int64(13)
?s?:=?strconv.FormatInt(x,?2)

?fmt.Println(s)
}

1101

or

package?main

import?(
?"fmt"
?"math/big"
)

func?main()?{
?x?:=?big.NewInt(13)
?s?:=?fmt.Sprintf("%b",?x)

?fmt.Println(s)
}

1101

fn?main()?{
????let?x?=?13;
????let?s?=?format!("{:b}",?x);
????
????println!("{}",?s);
}

1101

77. SComplex number

Declare a complex x and initialize it with value (3i - 2). Then multiply it by i.

復(fù)數(shù)

package?main

import?(
?"fmt"
?"reflect"
)

func?main()?{
?x?:=?3i?-?2
?x?*=?1i

?fmt.Println(x)
?fmt.Print(reflect.TypeOf(x))
}

(-3-2i)
complex128

extern?crate?num;
use?num::Complex;

fn?main()?{
????let?mut?x?=?Complex::new(-2,?3);
????x?*=?Complex::i();
????println!("{}",?x);
}

-3-2i

78. "do while" loop

Execute a block once, then execute it again as long as boolean condition c is true.

循環(huán)執(zhí)行

package?main

import?(
?"fmt"
?"math/rand"
)

func?main()?{
?for?{
??x?:=?rollDice()
??fmt.Println("Got",?x)
??if?x?==?3?{
???break
??}

?}
}

func?rollDice()?int?{
?return?1?+?rand.Intn(6)
}

Go has no do while loop, use the for loop, instead.

Got?6
Got?4
Got?6
Got?6
Got?2
Got?1
Got?2
Got?3

or

package?main

import?(
?"fmt"
?"math/rand"
)

func?main()?{
?for?done?:=?false;?!done;?{
??x?:=?rollDice()
??fmt.Println("Got",?x)
??done?=?x?==?3
?}
}

func?rollDice()?int?{
?return?1?+?rand.Intn(6)
}

Got?6
Got?4
Got?6
Got?6
Got?2
Got?1
Got?2
Got?3

loop?{
????doStuff();
????if?!c?{?break;?}
}

Rust has no do-while loop with syntax sugar. Use loop and break.

79. Convert integer to floating point number

Declare floating point number y and initialize it with the value of integer x .

整型轉(zhuǎn)浮點(diǎn)型

聲明浮點(diǎn)數(shù)y并用整數(shù)x的值初始化它。

package?main

import?(
?"fmt"
?"reflect"
)

func?main()?{
?x?:=?5
?y?:=?float64(x)

?fmt.Println(y)
?fmt.Printf("%.2f\n",?y)
?fmt.Println(reflect.TypeOf(y))
}

5
5.00
float64

fn?main()?{
????let?i?=?5;
????let?f?=?i?as?f64;
????
????println!("int?{:?},?float?{:?}",?i,?f);
}

int?5,?float?5.0

80. Truncate floating point number to integer

Declare integer y and initialize it with the value of floating point number x . Ignore non-integer digits of x . Make sure to truncate towards zero: a negative x must yield the closest greater integer (not lesser).

浮點(diǎn)型轉(zhuǎn)整型

package?main

import?"fmt"

func?main()?{
?a?:=?-6.4
?b?:=?6.4
?c?:=?6.6
?fmt.Println(int(a))
?fmt.Println(int(b))
?fmt.Println(int(c))
}

-6
6
6

fn?main()?{
????let?x?=?41.59999999f64;
????let?y?=?x?as?i32;
????println!("{}",?y);
}

41