Rust HashMap Key-Value Removal & Printing

Last update on December 21 2024 10:21:36 (UTC/GMT +8 hours)

Write a Rust program to remove a key-value pair from a HashMap and print the HashMap after removal.

Sample Solution:

Rust Code:

use std::collections::HashMap; // Import the HashMap type from the standard library

fn main() {
    // Create a HashMap to store key-value pairs
    let mut my_map: HashMap<&str, i32> = HashMap::new(); // Key: &str (string slice), Value: i32

    // Insert some key-value pairs into the HashMap
    my_map.insert("a", 1);
    my_map.insert("b", 2);
    my_map.insert("c", 3);

    // Print the original HashMap
    println!("Original HashMap: {:?}", my_map);

    // Define the key to remove from the HashMap
    let key_to_remove = "b";

    // Remove the key-value pair from the HashMap
    let removed_value = my_map.remove(key_to_remove);

    // Print the HashMap after removal
    match removed_value {
        Some(_) => println!("HashMap after removing key '{}': {:?}", key_to_remove, my_map), // If the key existed and was removed, print the updated HashMap
        None => println!("Key '{}' does not exist in the HashMap.", key_to_remove), // If the key did not exist, print a message
    }
}

Output:

Original HashMap: {"c": 3, "a": 1, "b": 2}
HashMap after removing key 'b': {"c": 3, "a": 1}

Explanation:

Here is a brief explanation of the above Rust code:

• use std::collections::HashMap;: This line imports the "HashMap" type from the standard library, allowing us to use HashMaps in our code.
• fn main() { ... }: This line defines the main function, which is the entry point of the Rust program.
• let mut my_map: HashMap<&str, i32> = HashMap::new();: This line creates an empty HashMap named 'my_map' with keys of type &str (string slice) and values of type i32.
• my_map.insert("a", 1);: This line inserts a key-value pair into the 'my_map' HashMap, where the key is the string slice "a" and the value is the integer 1. Similar lines insert additional key-value pairs.
• println!("Original HashMap: {:?}", my_map);: This line prints the original HashMap before any removals are made.
• let key_to_remove = "b";: This line defines the key that we want to remove from the HashMap.
• let removed_value = my_map.remove(key_to_remove);: This line removes the key-value pair associated with the specified key from the HashMap using the" remove()" method and stores the removed value, if any, in the 'removed_value' variable.
• match removed_value { ... }: This line starts a "match" statement to handle the result of removing the key-value pair:
• If the key existed and was removed (Some(_)), it prints the updated HashMap after removal.
• If the key did not exist (None), it prints a message indicating that the key does not exist in the HashMap.

Rust Code Editor:

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