Advent 2023 Day 11

advent_of_code_2023/day11/main2.rs

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+use std::fs::read_to_string;
+
+fn walk_row(distance_map: &Vec<(usize, usize)>, start: usize, end: usize) -> usize {
+    let mut distance: usize = 0;
+    let start_index = if start < end { start } else { end };
+    let end_index = if start > end { start } else { end };
+
+    for index in start_index..end_index {
+        distance += distance_map[index].0;
+    }
+
+    distance
+}
+
+fn walk_col(distance_map: &Vec<Vec<(usize, usize)>>, col: usize, start: usize, end: usize) -> usize {
+    let mut distance = 0;
+    let start_index = if start < end { start } else { end };
+    let end_index = if start > end { start } else { end };
+
+    for index in start_index..end_index {
+        distance += distance_map[index][col].1;
+    }
+
+    distance
+}
+
+fn main() {
+    let expansion: usize = 1_000_000;
+    let input = read_to_string("input.txt").unwrap();
+    let starmap = input.lines().map(|line| {
+        let mut vec: Vec<u8> = Vec::new();
+        vec.extend_from_slice(line.as_bytes());
+        vec
+    }).collect::<Vec<_>>();
+
+    let mut distance_map = starmap.iter().map(|line| {
+        vec![(1 as usize, 1 as usize); line.len()]
+    }).collect::<Vec<_>>();
+
+    for index in 0..starmap.len() {
+        if starmap[index].iter().filter(|ch| { **ch == b'#' }).count() == 0 {
+            for distance in distance_map[index].iter_mut() {
+                distance.1 *= expansion;
+            }
+        }
+    }
+
+    let mut index = 0;
+    loop {
+        if index >= starmap[0].len() {
+            break;
+        }
+
+        let mut sum = 0;
+        for line in &starmap {
+            if line[index] == b'#' {
+                sum += 1;
+            }
+        }
+
+        if sum == 0 {
+            for idx in 0..distance_map.len() {
+                distance_map[idx][index].0 *= expansion;
+            }
+        }
+
+        index += 1;
+    }
+
+    let mut stars: Vec<(usize, usize)> = Vec::new();
+    for row in 0..starmap.len() {
+        for col in 0..starmap[row].len() {
+            if starmap[row][col] == b'#' {
+                stars.push((row, col));
+            }
+        }
+    }
+
+    let mut sum_difference = 0;
+    for start_idx in 0..stars.len() {
+        for inner_idx in start_idx..stars.len() {
+            sum_difference += walk_col(&distance_map, stars[start_idx].1, stars[start_idx].0, stars[inner_idx].0);
+            sum_difference += walk_row(&distance_map[stars[start_idx].0], stars[start_idx].1, stars[inner_idx].1);
+        }
+    }
+
+    println!("Sum of ranges: {}", sum_difference);
+}