AdventOfCode/y2015/src/days/d12.rs

pub fn process_part1(input: &str) -> i32 {
    let mut sum = 0;
    let mut number = String::new();
    for &byte in input.as_bytes() {
        if byte == b'-' || byte.is_ascii_digit() {
            number.push(byte as char);
        } else if !number.is_empty() {
            sum += number.parse::<i32>().unwrap();
            number.clear();
        }
    }
    sum
}

pub fn process_part2(input: &str) -> i32 {
    let red_indices = input
        .match_indices("red")
        .map(|(idx, _)| idx)
        .collect::<Vec<usize>>();
    let mut red_objects = Vec::new();
    let mut last_range = (0, 0);
    for idx in red_indices {
        if idx > last_range.0 && idx < last_range.1 {
            continue;
        }
        let (left, right) = input.split_at(idx);
        let open = find_open(left);
        let close = find_close(right) + idx as u32;
        let range = (open as usize, close as usize + 1);
        last_range = range;
        if !red_objects.contains(&range) {
            red_objects.push(range);
        }
    }
    red_objects.reverse();
    // remove overlaps not caught during creation
    let mut last_range = (0, 0);
    let mut no_overlap = Vec::new();
    for range in red_objects.clone() {
        if last_range.0 < range.0 && last_range.1 > range.1 {
            continue;
        }
        last_range = range;
        no_overlap.push(range);
    }
    let mut unreded_input = input.to_owned();
    for range in no_overlap {
        unreded_input.replace_range(range.0..range.1, "0");
    }
    process_part1(&unreded_input)
}

fn find_open(string: &str) -> u32 {
    let mut bytes = string.as_bytes().to_vec();
    bytes.reverse();
    let length = bytes.len();
    // count of traversed objects
    // increments when seeing } decrements when seeing {
    // while == 0, potentially inside an object
    // while > 0 peeking inside another object
    // when < 0 left object red is inside of
    // when == 0 and encountered [ then inside array
    let mut curly_count = 0;
    let mut square_count = 0;
    let mut idx = length - 1;
    for byte in bytes {
        if byte == b'}' {
            curly_count += 1
        } else if byte == b'{' {
            curly_count -= 1
        } else if byte == b'[' {
            square_count -= 1;
        } else if byte == b']' {
            square_count += 1;
        }
        if square_count < 0 {
            return length as u32 - 1;
        }
        if curly_count < 0 || idx == 0 {
            break;
        }
        idx -= 1;
    }
    if curly_count < 0 {
        idx as u32
    } else {
        length as u32
    }
}

fn find_close(string: &str) -> u32 {
    let bytes = string.as_bytes().to_vec();
    let length = bytes.len();
    // count of traversed objects
    // increments when seeing { decrements when seeing }
    // while == 0, potentially inside an object
    // while > 0 peeking inside another object
    // when < 0 left object red is inside of
    // when == 0 and encountered ] then inside array
    let mut curly_count = 0;
    let mut square_count = 0;
    let mut idx = 0;
    for byte in bytes {
        if byte == b'}' {
            curly_count -= 1
        } else if byte == b'{' {
            curly_count += 1
        } else if byte == b']' {
            square_count -= 1;
        } else if byte == b'[' {
            square_count += 1;
        }
        if square_count < 0 {
            return 0;
        }
        if curly_count < 0 || idx == length {
            break;
        }
        idx += 1;
    }
    if curly_count < 0 {
        idx as u32
    } else {
        0
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn part1() {
        let result_a = process_part1("[1,2,3]");
        let result_b = process_part1(r#"{"a":2,"b":4}"#);
        assert_eq!(result_a, 6);
        assert_eq!(result_b, 6);
        let result_a = process_part1("[[[3]]]");
        let result_b = process_part1(r#"{"a":{"b":4},"c":-1}"#);
        assert_eq!(result_a, 3);
        assert_eq!(result_b, 3);
        let result_a = process_part1(r#"{"a":[-1,1]}"#);
        let result_b = process_part1(r#"[-1,{"a":1}]"#);
        assert_eq!(result_a, 0);
        assert_eq!(result_b, 0);
        let result_a = process_part1("[]");
        let result_b = process_part1("{}");
        assert_eq!(result_a, 0);
        assert_eq!(result_b, 0);
    }

    #[test]
    fn part2() {
        //let result_a = process_part2("[1,2,3]");
        //let result_b = process_part2(r#"{"a":2,"b":4}"#);
        //assert_eq!(result_a, 6);
        //assert_eq!(result_b, 6);
        //let result_a = process_part2("[[[3]]]");
        //let result_b = process_part2(r#"{"a":{"b":4},"c":-1}"#);
        //assert_eq!(result_a, 3);
        //assert_eq!(result_b, 3);
        //let result_a = process_part2(r#"{"a":[-1,1]}"#);
        //let result_b = process_part2(r#"[-1,{"a":1}]"#);
        //assert_eq!(result_a, 0);
        //assert_eq!(result_b, 0);
        //let result_a = process_part2("[]");
        //let result_b = process_part2("{}");
        //assert_eq!(result_a, 0);
        //assert_eq!(result_b, 0);
        let result_a = process_part2(r#"[1,{"c":"red","b":2},3]"#);
        assert_eq!(result_a, 4);
        let result_a = process_part2(r#"{"d":"red","e":[1,2,3,4],"f":5}"#);
        assert_eq!(result_a, 0);
        let result_a = process_part2(r#"[1,"red",5]"#);
        assert_eq!(result_a, 6);
    }
}