//! [Problem 11](https://projecteuler.net/problem=11) solver.

#![warn(bad_style,
        unused, unused_extern_crates, unused_import_braces,
        unused_qualifications, unused_results)]

#![feature(iter_arith)]

#[macro_use(problem)] extern crate common;

const INPUT: &'static 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
";

fn compute(prod_len: usize) -> u32 


fn solve() -> String { compute(4).to_string() }

problem!("70600674", solve);

{
    let grid: Vec<Vec<u32>> = INPUT
        .trim()
        .lines()
        .map(|line| {
            line.split_whitespace().filter_map(|s| s.parse().ok()).collect()
        })
        .collect();

    let w = grid[0].len();
    let h = grid.len();

    let mut lines: Vec<Vec<_>> = vec![];
    // rows
    lines.extend((0 .. h).map(|y| (0 .. w).map(|x| (x, y)).collect()));
    // cols
    lines.extend((0 .. w).map(|x| (0 .. h).map(|y| (x, y)).collect()));
    // top 2 right diagonal
    lines.extend((0 .. w).map(|i| {
        let (x0, y0) = (i, 0);
        (0 .. w - x0).map(|j| (x0 + j, y0 + j)).collect()
    }));
    // left 2 bottom diagonal
    lines.extend((0 .. h - 1).map(|i| {
        let (x0, y0) = (0, i + 1);
        (0 .. h - y0).map(|j| (x0 + j, y0 + j)).collect()
    }));
    // top 2 left diagonal
    lines.extend((0 .. w).map(|i| {
        let (x0, y0) = (i, 0);
        (0 .. x0 + 1).map(|j| (x0 - j, y0 + j)).collect()
    }));
    // right 2 bottom diagonal
    lines.extend((0 .. h - 1).map(|i| {
        let (x0, y0) = (w - 1, i + 1);
        (0 .. h - y0).map(|j| (x0 - j, y0 + j)).collect()
    }));

    lines.iter()
        .map(|cells| {
            cells.windows(prod_len)
                .map(|ns| ns.iter().map(|&(x, y)| grid[y][x]).product())
                .max()
                .unwrap_or(0)
        }).max()
        .unwrap()
}