Rust Character Frequency Counter

Last update on December 21 2024 10:19:16 (UTC/GMT +8 hours)

Write a Rust program to count the frequency of characters in a string and store the result in a HashMap.

Sample Solution:

Rust Code:

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

fn main() {
    // Define the input string
    let input_string = "w3resource.com";

    // Create an empty HashMap to store character frequencies
    let mut char_frequency: HashMap<char, usize> = HashMap::new(); // Key: char, Value: usize

    // Iterate over each character in the input string
    for ch in input_string.chars() {
        // Check if the character is already present in the HashMap
        // If it is present, increment its frequency count
        // If it is not present, insert it into the HashMap with a frequency count of 1
        let count = char_frequency.entry(ch).or_insert(0);
        *count += 1;
    }

    // Print the HashMap containing character frequencies
    println!("Character Frequencies: {:?}", char_frequency);
}

Output:

Character Frequencies: {'e': 2, 'r': 2, '3': 1, 's': 1, 'c': 2, 'm': 1, '.': 1, 'u': 1, 'w': 1, 'o': 2}

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 input_string = "w3resource.com";: This line defines the input string for which we want to count the frequency of characters.
• let mut char_frequency: HashMap<char, usize> = HashMap::new();: This line creates an empty HashMap named char_frequency with keys of type char and values of type usize to store the frequency of characters.
• for ch in input_string.chars() { ... }: This line starts a loop to iterate over each character (ch) in the input string using the chars() method.
• let count = char_frequency.entry(ch).or_insert(0);: This line checks if the current character ch is already present in the char_frequency HashMap. If it is present, it returns a mutable reference to its frequency count (count). If it is not present, it inserts the character into the HashMap with a frequency count of 0 and returns a mutable reference to the newly inserted value.
• *count += 1;: This line increments the frequency count of the current character by 1 using the mutable reference obtained in the previous step.
• println!("Character Frequencies: {:?}", char_frequency);: Finally this line prints the HashMap containing the frequency of characters after iterating through the entire input string.

Rust Code Editor:

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