project euler problem 11

main.rs

const GRID_NUMBERS: &str = "\
08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08 \
49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00 \
81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65 \
52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91 \
22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80 \
24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50 \
32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70 \
67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21 \
24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72 \
21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95 \
78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92 \
16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57 \
86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58 \
19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40 \
04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66 \
88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69 \
04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36 \
20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16 \
20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54 \
01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48 ";

const GRID_SIZE: usize = 20;

fn parse(text: &str) -> Vec<u32> {
    let mut parsed: Vec<u32> = Vec::new();
    let mut tmp = String::new();    

    for c in text.chars() {
        if c == ' ' {
            let n = tmp.parse::<u32>().unwrap();
            parsed.push(n);
            tmp = "".to_string();
            continue
        }

        tmp.push(c);
    }
    parsed
}

fn take(array: &Vec<u32>, x: i32, y: i32) -> u32 {
    if x < 0 || y < 0 || x >= GRID_SIZE as i32|| y >= GRID_SIZE as i32{
        return 0
    }

    array[x as usize + y as usize * GRID_SIZE]
}

fn test(array: &Vec<u32>, x: usize, y: usize) -> u32 {
    let x = x as i32;
    let y = y as i32;    

    let mut grid_products: Vec<u32> = Vec::new();

    // horizontal
    grid_products.push(take(array, x ,y) * take(array, x+1, y) * take(array, x+2, y) * take(array, x+3, y));
    // vertical
    grid_products.push(take(array, x ,y) * take(array, x, y+1) * take(array, x, y+2) * take(array, x, y+3));
    // diagonal(left down)
    grid_products.push(take(array, x ,y) * take(array, x+1, y+1) * take(array, x+2, y+2) * take(array, x+3, y+3));
    // diagonal(right down)
    grid_products.push(take(array, x ,y) * take(array, x-1, y+1) * take(array, x-2, y+2) * take(array, x-3, y+3));

    let max = grid_products.into_iter().fold(0, |m, v| v.max(m));
    max
}

fn main() {
    let parsed = parse(GRID_NUMBERS);
    let mut max = 0;
    
    for x in 0..GRID_SIZE {
        for y in 0..GRID_SIZE {
            let local_max = test(&parsed, x, y);
            if local_max > max {
                max = local_max;
            }
        }
    }

    println!("{:?}", max);
}