128 lines
3.2 KiB
Rust
128 lines
3.2 KiB
Rust
use std::fs::File;
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use std::io::{BufRead, BufReader};
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fn calc_map_from_serial_number(serial_number: i32) -> [[i32; 300]; 300] {
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let mut result = [[0i32; 300]; 300];
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for i in 0..300 {
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for j in 0..300 {
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let rack_id = i + 10;
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let power = ((rack_id * j) + serial_number) * rack_id;
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let hundreds = power.to_string().as_str().chars().rev().nth(2).unwrap();
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result[i as usize][j as usize] = (hundreds as i32) - 48 - 5;
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}
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}
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result
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}
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fn find_max_sum(map: &[[i32; 300]; 300], subsize: usize) -> (usize, usize, i32) {
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let presums = precalculate_sums(&map, subsize);
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let mut x = 0;
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let mut y = 0;
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let mut sum = 0;
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for i in 0..(300 - subsize) {
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for j in 0..(300 - subsize) {
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let mut new_sum = 0;
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for s in 0..subsize {
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new_sum += presums[i + s][j];
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}
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if new_sum > sum {
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sum = new_sum;
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x = i;
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y = j;
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}
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}
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}
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(x, y, sum)
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}
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fn precalculate_sums(map: &[[i32; 300]; 300], subsize: usize) -> [[i32; 300]; 300] {
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let mut result = [[0i32; 300]; 300];
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for i in 0..300 {
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for j in 0..(300 - subsize) {
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for s in 0..subsize {
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result[i][j] += map[i][j + s];
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}
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}
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}
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result
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}
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fn find_variable_max_sum(map: &[[i32; 300]; 300]) -> (usize, usize, i32, usize) {
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let mut x = 0;
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let mut y = 0;
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let mut size = 0;
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let mut sum = 0;
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for i in 1..=300 {
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let (new_x, new_y, new_sum) = find_max_sum(map, i);
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if new_sum == 0 {
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break;
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}
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if new_sum > sum {
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size = i;
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sum = new_sum;
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x = new_x;
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y = new_y;
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}
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}
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(x, y, sum, size)
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}
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fn main() {
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let mut line = String::new();
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BufReader::new(File::open("input").unwrap())
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.read_line(&mut line)
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.unwrap();
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let serial_number = line.trim().parse::<i32>().unwrap();
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let map = calc_map_from_serial_number(serial_number);
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let (x, y, sum) = find_max_sum(&map, 3);
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println!(
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"maximum sum coordinate of ({}, {}) with sum of {}",
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x, y, sum
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);
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let (x, y, sum, size) = find_variable_max_sum(&map);
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println!(
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"maximum variable sum found at ({}, {}) sum {} with size of {}",
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x, y, sum, size
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);
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_part_one() {
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let serial_number = 18;
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let map = calc_map_from_serial_number(serial_number);
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let (x, y, sum) = find_max_sum(&map, 3);
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assert_eq!(x, 33);
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assert_eq!(y, 45);
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assert_eq!(sum, 29);
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}
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#[test]
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fn test_part_two_for_18() {
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let map = calc_map_from_serial_number(18);
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let (x, y, sum, size) = find_variable_max_sum(&map);
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assert_eq!(x, 90);
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assert_eq!(y, 269);
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assert_eq!(sum, 113);
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assert_eq!(size, 16);
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}
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#[test]
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fn test_part_two_for_42() {
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let map = calc_map_from_serial_number(42);
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let (x, y, sum, size) = find_variable_max_sum(&map);
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assert_eq!(x, 232);
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assert_eq!(y, 251);
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assert_eq!(sum, 119);
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assert_eq!(size, 12);
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}
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}
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