【Rust基础】排序和分组

排序

简单排序

• 整数排序

  #[test]
  fn test_sort(){
      let mut list = vec![1, 5, 3, 2, 4];
      list.sort(); //✔
      assert_eq!(list, vec![1, 2, 3, 4, 5]);
  }
  

• 小数排序

  #[test]
  fn test_sort(){
      let mut list = vec![1, 5, 3, 2, 4];
      //❌ 不能直接使用sort，因为f32和f64未实现Ord trait
      //list.sort();
      //✔ 可以使用sort_by，自定义排序规则
      list.sort_by(|a, b| a.partial_cmp(b).unwrap());
    	assert_eq!(list, vec![1., 2., 3., 4., 5.]);
  }
  

  💡partial_cmp和total_cmp：total_cmp接受NAN的比较，partial_cmp如未处理NAN会paninc；

• struct排序

  #[test]
  fn test_struct_sort() {
      #[derive(Debug)]
      struct Person {
          name: String,
          age: i32,
      }
      let mut persons = vec![
          Person {
              name: "Alice".to_string(),
              age: 25,
          },
          Person {
              name: "Bob".to_string(),
              age: 30,
          },
          Person {
              name: "Charlie".to_string(),
              age: 20,
          },
      ];
  
      persons.sort_by(|a, b| a.age.cmp(&b.age));
      println!("sorted_persons: {:?}", persons);
      // sorted_persons: [Person { name: "Charlie", age: 20 }, Person { name: "Alice", age: 25 }, Person { name: "Bob", age: 30 }]
  }
  

分组

使用HashMap

#[test]
fn test_group() {
	// 按奇数和偶数分组
    let list = vec![1, 2, 3, 4, 5];
    let mut group = HashMap::new();
    list.iter().for_each(|x| {
        if x % 2 == 0 {
            group.entry("even").or_insert(vec![]).push(*x);
        } else {
            group.entry("odd").or_insert(vec![]).push(*x);
        }
    });
    println!("group:{:?}", group);
    // group:{"odd": [1, 3, 5], "even": [2, 4]}
}

使用itertools

#[test]
fn test_group_with_iter_tools() {
	// 按奇数和偶数分组
    let list = vec![1, 2, 3, 4, 5];
    let group = list
        .iter()
        .into_group_map_by(|&x| if x % 2 == 0 { "even" } else { "odd" });
    println!("group:{:?}", group);
}
//group:{"odd": [1, 3, 5], "even": [2, 4]}