How to count the Number of Occurrences of Specific Item in the Vector in Rust - Step by Step Examples

How to count the Number of Occurrences of Specific Item in the Vector in Rust ?

Answer

To count the number of occurrences of a specific item in a vector in Rust, you can use the iter method combined with the filter method and the count method.


✐ Examples

1 Count Number of Occurrences of a Specific Number in a Numeric Vector

In this example,

  1. We create a vector named vec with a set of numerical values using the vec![] macro.
  2. We define a variable item that holds the value we want to count in the vector.
  3. We use the iter method on the vector vec to create an iterator over the elements of the vector.
  4. We then use the filter method on the iterator to retain only the elements that match item. The closure |&x| x == &item is used to compare each element x with item.
  5. We call the count method on the filtered iterator to count the number of matching elements.
  6. Finally, we print the result to standard output using the println! macro.

Rust Program

fn main() {
    let vec = vec![1, 2, 3, 2, 2, 4, 5, 2];
    let item = 2;
    let count = vec.iter().filter(|&x| x == &item).count();
    println!("{}", count);
}

Output

4

2 Count Number of Occurrences of a Specific String in a Character Vector

In this example,

  1. We create a vector named char_vec with a set of string values using the vec![] macro.
  2. We define a variable str_item that holds the string we want to count in the vector.
  3. We use the iter method on the vector char_vec to create an iterator over the elements of the vector.
  4. We then use the filter method on the iterator to retain only the elements that match str_item. The closure |&x| x == &str_item is used to compare each element x with str_item.
  5. We call the count method on the filtered iterator to count the number of matching elements.
  6. Finally, we print the result to standard output using the println! macro.

Rust Program

fn main() {
    let char_vec = vec!["apple", "banana", "apple", "cherry", "banana", "apple"];
    let str_item = "apple";
    let count = char_vec.iter().filter(|&x| x == &str_item).count();
    println!("{}", count);
}

Output

3

3 Count Number of Occurrences of a Specific Boolean Value in a Boolean Vector

In this example,

  1. We create a vector named bool_vec with a set of boolean values using the vec![] macro.
  2. We define a variable bool_item that holds the boolean value we want to count in the vector.
  3. We use the iter method on the vector bool_vec to create an iterator over the elements of the vector.
  4. We then use the filter method on the iterator to retain only the elements that match bool_item. The closure |&x| x == &bool_item is used to compare each element x with bool_item.
  5. We call the count method on the filtered iterator to count the number of matching elements.
  6. Finally, we print the result to standard output using the println! macro.

Rust Program

fn main() {
    let bool_vec = vec![true, false, true, true, false, true, false];
    let bool_item = true;
    let count = bool_vec.iter().filter(|&x| x == &bool_item).count();
    println!("{}", count);
}

Output

4

Summary

In this tutorial, we learned How to count the Number of Occurrences of Specific Item in the Vector in Rust language with well detailed examples.


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