Day 11: Finding a max sum of an area

1 files changed, 50 insertions, 2 deletions

diff --git a/src/bin/day_11.rs b/src/bin/day_11.rs
index cf9c35f..0e458a3 100644
--- a/src/bin/day_11.rs
+++ b/src/bin/day_11.rs
@@ -2,17 +2,65 @@ extern crate advent_of_code_2018;
 use advent_of_code_2018::*;
 
 use std::error::Error;
-use std::path::PathBuf;
+use std::i32;
 
 // cargo watch -cs "cargo run --release --bin day_11"
 
 fn main() -> Result<(), Box<Error>> {
-    let input = read_file(&PathBuf::from("inputs/11.txt"))?;
+    let input = 1723;
 
     println!("Input: {:?}", input);
 
+    let powers = precompute_powers(input);
 
+    let power_per_size = (1..300).map(|size| {
+        (1..302-size).map(|left| {
+            (1..302-size).map(|top| {
+                (power_for_block(left, top, size, &powers), (left, top, size))
+            }).max_by_key(|(p, _)| *p).unwrap()
+        }).max_by_key(|(p, _)| *p).unwrap()
+    }).collect::<Vec<_>>();
 
+    let (max_power_at_size_3, coordinate_at_size_3) = power_per_size[2]; // index from 0 vs 1
+    debug!(max_power_at_size_3);
+    debug!(coordinate_at_size_3);
+
+    let (max_power, coordinate) = power_per_size.iter().max_by_key(|(p, _)| p).unwrap();
+    
+    debug!(max_power);
+    debug!(coordinate);
 
     Ok(())
 }
+
+fn power_for_block(left: i32, top: i32, size: i32, powers: &[[i32;300];300]) -> i32 {
+    (left..left+size).map(|x| {
+        (top..top+size).map(|y| {
+            powers[x as usize - 1][y as usize - 1]
+        }).sum::<i32>()
+    }).sum()
+}
+
+fn precompute_powers(input: i32) -> [[i32;300];300] {
+    let mut powers: [[i32;300];300] = [[0;300];300];
+    for x in 1..301 {
+        for y in 1..301 {
+            powers[x as usize - 1][y as usize - 1] = power_from_coordinates(x, y, input);
+        }
+    }
+    powers
+}
+
+fn power_from_coordinates(x: i32, y: i32, input: i32) -> i32 {
+    let rack_id = x + 10;
+    ((((rack_id * y) + input) * rack_id / 100) % 10) - 5
+}
+
+
+#[test]
+fn power_from_coord_example() {
+    assert_eq!(power_from_coordinates(3, 5, 8), 4);
+    assert_eq!(power_from_coordinates(122, 79, 57), -5);
+    assert_eq!(power_from_coordinates(217,196, 39), 0);
+    assert_eq!(power_from_coordinates(101, 153, 71), 4);
+}