我有一个向量,其中的元素是 (String, String)
。如何随机选择其中一个元素?
使用choose_multiple
方法:
use rand::seq::SliceRandom; // 0.7.2
fn main() {
let samples = vec!["hi", "this", "is", "a", "test!"];
let sample: Vec<_> = samples
.choose_multiple(&mut rand::thread_rng(), 1)
.collect();
println!("{:?}", sample);
}
WeightedIndex
use rand::prelude::*;
use rand::distributions::WeightedIndex;
let choices = ['a', 'b', 'c'];
let weights = [2, 1, 1];
let dist = WeightedIndex::new(&weights).unwrap();
let mut rng = thread_rng();
for _ in 0..100 {
// 50% chance to print 'a', 25% chance to print 'b', 25% chance to print 'c'
println!("{}", choices[dist.sample(&mut rng)]);
}
let items = [('a', 0), ('b', 3), ('c', 7)];
let dist2 = WeightedIndex::new(items.iter().map(|item| item.1)).unwrap();
for _ in 0..100 {
// 0% chance to print 'a', 30% chance to print 'b', 70% chance to print 'c'
println!("{}", items[dist2.sample(&mut rng)].0);
}
如果你想选择多个元素,那么random_choice 库可能适合你:
extern crate random_choice;
use self::random_choice::random_choice;
fn main() {
let mut samples = vec!["hi", "this", "is", "a", "test!"];
let weights: Vec<f64> = vec![5.6, 7.8, 9.7, 1.1, 2.0];
let number_choices = 100;
let choices = random_choice().random_choice_f64(&samples, &weights, number_choices);
for choice in choices {
print!("{}, ", choice);
}
}
rand
crate):let mut vec = vec![0,1,2,3,4,5,6,7,8,9];
let index = (rand::random::<f32>() * vec.len() as f32).floor() as usize;
let value = vec.remove( index );
println!("index: {} value: {}", index, value);
println!("{:?}", vec);
remove(index)
函数可以移除指定索引处的值(并将其后面的所有元素向左移动),然后返回该索引处的值(文档)。请注意,HTML标签应保留而不进行解释。
通过使用rng.gen_range和vec.get()的索引方法,还可以获取随机值。这也可以防止借用该值(在vec.choose()方法中会发生此情况)。
fn main() {
let mut rng = rand::thread_rng();
let my_strings : Vec<&str> = vec!["a", "b", "c"];
let random_string_index: usize = rng.gen_range(0..my_strings.len());
let string = my_strings[random_string_index];
println!("{:?}", string);
}