day 11 solution

2018/day11/Cargo.lock

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+[[package]]
+name = "day11"
+version = "0.1.0"
+

2018/day11/Cargo.toml

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+[package]
+name = "day11"
+version = "0.1.0"
+authors = ["Andrew Coleman <penguincoder@gmail.com>"]
+edition = "2018"
+
+[dependencies]

2018/day11/input

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+5468

2018/day11/src/main.rs

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+use std::fs::File;
+use std::io::{BufRead, BufReader};
+use std::iter::Iterator;
+
+fn calc_map_from_serial_number(serial_number: i32) -> [[i32; 300]; 300] {
+    let mut result = [[0i32; 300]; 300];
+    for i in 0..300 {
+        for j in 0..300 {
+            let rack_id = i + 10;
+            let power = ((rack_id * j) + serial_number) * rack_id;
+            let hundreds = power.to_string().as_str().chars().rev().nth(2).unwrap();
+            result[i as usize][j as usize] = (hundreds as i32) - 48 - 5;
+        }
+    }
+    result
+}
+
+fn find_max_sum(map: &[[i32; 300]; 300], subsize: usize) -> (usize, usize, i32) {
+    let presums = precalculate_sums(&map, subsize);
+    let mut x = 0;
+    let mut y = 0;
+    let mut sum = 0;
+    for i in 0..(300 - subsize) {
+        for j in 0..(300 - subsize) {
+            let mut new_sum = 0;
+            for s in 0..subsize {
+                new_sum += presums[i + s][j];
+            }
+            if new_sum > sum {
+                sum = new_sum;
+                x = i;
+                y = j;
+            }
+        }
+    }
+
+    (x, y, sum)
+}
+
+fn precalculate_sums(map: &[[i32; 300]; 300], subsize: usize) -> [[i32; 300]; 300] {
+    let mut result = [[0i32; 300]; 300];
+    for i in 0..300 {
+        for j in 0..(300 - subsize) {
+            for s in 0..subsize {
+                result[i][j] += map[i][j + s];
+            }
+        }
+    }
+
+    result
+}
+
+fn find_variable_max_sum(map: &[[i32; 300]; 300]) -> (usize, usize, i32, usize) {
+    let mut x = 0;
+    let mut y = 0;
+    let mut size = 0;
+    let mut sum = 0;
+    for i in 1..=300 {
+        let (new_x, new_y, new_sum) = find_max_sum(map, i);
+        if new_sum == 0 { break; }
+        if new_sum > sum {
+            size = i;
+            sum = new_sum;
+            x = new_x;
+            y = new_y;
+        }
+    }
+
+    (x, y, sum, size)
+}
+
+fn main() {
+    let mut line = String::new();
+    BufReader::new(File::open("input").unwrap())
+        .read_line(&mut line)
+        .unwrap();
+    let serial_number = line.trim().parse::<i32>().unwrap();
+
+    let map = calc_map_from_serial_number(serial_number);
+    let (x, y, sum) = find_max_sum(&map, 3);
+    println!("maximum sum coordinate of ({}, {}) with sum of {}", x, y, sum);
+
+    let (x, y, sum, size) = find_variable_max_sum(&map);
+    println!("maximum variable sum found at ({}, {}) sum {} with size of {}", x, y, sum, size);
+}