CodeWars/5kyu/my_smallest_code_interpreter_bf/solution.rs

use std::collections::HashMap;

fn find_left(instructions: &[u8], index: usize) -> usize {
    let mut result = index - 1;
    let mut count = 1;

    while count != 0 {
        if instructions[result] == ']' as u8 {
            count += 1;
        } else if instructions[result] == '[' as u8 {
            count -= 1;
        }

        result -= 1;
    }

    result + 1
}

fn find_right(instructions: &[u8], index: usize) -> usize {
    let mut result = index + 1;
    let mut count = 1;

    while count != 0 {
        if instructions[result] == '[' as u8 {
            count += 1;
        } else if instructions[result] == ']' as u8 {
            count -= 1;
        }

        result += 1;
    }

    result - 1
}

fn brain_luck(code: &str, input: Vec<u8>) -> Vec<u8> {
    let instructions = code.as_bytes();

    let mut result = Vec::<u8>::new();
    let mut tape = HashMap::<i64, i16>::new();
    let mut i = 0;
    let mut tape_i = 0;
    let mut input_i = 0;

    while i < instructions.len() {
        match instructions[i] as char {
            '>' => tape_i += 1,
            '<' => tape_i -= 1,
            '+' => {
                tape.insert(tape_i, (tape.get(&tape_i).unwrap_or(&0) + 1) % 256);
                ()
            }
            '-' => {
                let new_value = tape.get(&tape_i).unwrap_or(&0) - 1;
                tape.insert(tape_i, if new_value < 0 { 255 } else { new_value });
                ()
            }
            '.' => {
                result.push(*tape.get(&tape_i).unwrap_or(&0) as u8);
                ()
            }
            ',' => {
                tape.insert(tape_i, input[input_i] as i16);
                input_i += 1;
                ()
            }
            '[' => {
                if *tape.get(&tape_i).unwrap_or(&0) == 0 {
                    i = find_right(instructions, i);
                }
                ()
            }
            ']' => {
                if *tape.get(&tape_i).unwrap_or(&0) != 0 {
                    i = find_left(instructions, i);
                }
                ()
            }
            _ => {}
        }

        i += 1;
    }
    result
}