我有一个向量,其中元素是(String, String)
。我如何随机选择其中一个元素?
答案 0 :(得分:23)
use rand::seq::SliceRandom; // 0.6.5
fn main() {
let vs = vec![0, 1, 2, 3, 4];
println!("{:?}", vs.choose(&mut rand::thread_rng()));
}
答案 1 :(得分:5)
use rand::seq::SliceRandom; // 0.6.5
fn main() {
let samples = vec!["hi", "this", "is", "a", "test!"];
let sample: Vec<_> = samples
.choose_multiple(&mut rand::thread_rng(), 1)
.collect();
println!("{:?}", sample);
}
答案 2 :(得分:3)
如果你想选择多个元素,那么 random_choice 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);
}
}
答案 3 :(得分:2)
Another choice for weighted sampling that is already included in the rand
crate is WeightedIndex
, which has an example:
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); }
答案 4 :(得分:0)
如果您还想删除所选元素,这是一种方法(使用rand
板条箱):
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)
删除index
处的值(将其后的所有元素向左移动)并返回index
(docs)处的值。 / p>