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fn main() {
let input = "\
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";
let input_split = input.split_whitespace();
let input_as_num: Vec<i32> = input_split.map(|x|
match i32::from_str_radix(x, 10) {
Ok(v) => v,
Err(u) => { println!("Garbage in input: {}", u); 0 }
}
).collect();
const GRID_SIZE: usize = 20;
const ANSWER_LENGTH: usize = 4;
let element_at = |x:usize, y:usize| {
return input_as_num[y * GRID_SIZE + x];
};
let stride_sum = |x:usize, y:usize, x_stride:i32, y_stride:i32| {
let mut answer = 1;
for current in 0..ANSWER_LENGTH {
answer *= element_at(((x as i32) + x_stride * (current as i32)) as usize,
((y as i32) + y_stride * (current as i32)) as usize);
}
return answer;
};
let mut greatest_answer = 0;
for y in 0..(GRID_SIZE - ANSWER_LENGTH + 1) {
for x in 0..GRID_SIZE {
//DOWN
{
let answer = stride_sum(x, y, 0, 1);
if answer > greatest_answer { greatest_answer = answer; }
}
//DOWN+LEFT
if x >= (ANSWER_LENGTH-1) {
let answer = stride_sum(x, y, -1, 1);
if answer > greatest_answer { greatest_answer = answer; }
}
//DOWN+RIGHT and RIGHT
if x <= (GRID_SIZE-ANSWER_LENGTH) {
let down_right_answer = stride_sum(x, y, 1, 1);
if down_right_answer > greatest_answer { greatest_answer = down_right_answer; }
let right_answer = stride_sum(x, y, 1, 0);
if right_answer > greatest_answer { greatest_answer = right_answer; }
}
}
}
println!("{}", greatest_answer);
}