LeetCode

This repository contains solutions to coding problems from LeetCode, implemented in Rust.
The goal is to practice problem-solving skills, improve Rust proficiency, and maintain high code quality.

Useful tricks

1. Use String::as_bytes to efficiently access characters in a string.
2. Use bitwise flags for tracking multiple boolean states:

   let mut flags = 0_u32;
   flags |= 1 << i; // Set flag i
   flags ^= 1 << i; // Clear flag i

3. Use array indexing instead of HashMap for small fixed-size data sets to improve performance:

   let mut counts = [0; 26]; // For lowercase letters 'a' to 'z'
   for &b in s.into_bytes() {
        counts[(b - b'a') as usize] += 1;
   }

4. Using linear search in small arrays is efficient enough and simple. No need for complex data structures.
5. Use bitwise operations to count unique characters in a string:

   let mut mask = 0_u32;
   for &b in s.into_bytes() {
       mask |= 1 << (b - b'a');
   }
   let unique_count = mask.count_ones();

6. Use faster hasher:

    use std::hash::{BuildHasherDefault, DefaultHasher};
    let mut map: HashMap<_, _, _> =
        HashMap::with_capacity_and_hasher(26, BuildHasherDefault::<DefaultHasher>::default());