not the prettiest but i got it done. i figured out the right approach by part 2

day11/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day11"
+version = "0.1.0"

day11/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day11"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day11/src/main.rs

@@ -0,0 +1,183 @@
+use std::iter::*;
+use std::fs;
+use std::env;
+
+#[derive(Debug, Copy, Clone, PartialEq)]
+struct Coord {x: i64, y: i64}
+fn pt(x:i64, y:i64) -> Coord { Coord { x, y } }
+
+struct Grid<T: Copy> { g: Vec<Vec<T>> }
+
+impl<T: Copy> Grid<T> {
+    fn get(&self, r: Coord) -> Option<T> {
+        if r.y < 0 || r.y >= self.g.len() as i64 {
+            return None;
+        }
+        if r.x < 0 || r.x >= self.g[0].len() as i64 {
+            return None;
+        }
+        Some(self.g[r.y as usize][r.x as usize])
+    }
+    fn set(&mut self, r: Coord, value: T) {
+        if r.y < 0 || r.y >= self.g.len() as i64 {
+            return ();
+        }
+        if r.x < 0 || r.x >= self.g[0].len() as i64 {
+            return ();
+        }
+        self.g[r.y as usize][r.x as usize] = value;
+    }
+}
+
+fn main() {
+    println!("Hello, AoC day 11!");
+
+    let args: Vec<String> = env::args().collect();
+    if args.len() != 2 {
+        println!("wrong number of arguments!");
+        std::process::exit(1);
+    }
+
+    let file_path = &args[1];
+
+    let contents = fs::read_to_string(file_path)
+        .expect("Should have been able to read the file");
+
+
+    let mut grid = Grid::<char> { g: Vec::new() };
+    let mut rows_to_expand: Vec<bool> = Vec::new();
+    let mut columns_to_expand: Vec<bool> = Vec::new();
+    for _y in contents.lines() {
+        rows_to_expand.push(true);
+    }
+    for _x in contents.lines().nth(0).expect("there's gotta be a first line").chars() {
+        columns_to_expand.push(true);
+    }
+
+    // let's build that grid
+    for (y, line) in contents.lines().enumerate() {
+
+        let mut row = Vec::new();
+        for (x, c) in line.chars().enumerate() {
+            if c != '.' {
+                rows_to_expand[y] = false;
+                columns_to_expand[x] = false;
+            }
+            row.push(c);
+        }
+        grid.g.push(row);
+    }
+    println!("starting grid:");
+    print_map(&grid);
+
+
+    println!("expanding these:");
+    println!("rows: {rows_to_expand:?}");
+    println!("columns: {columns_to_expand:?}");
+
+    let mut offset=0;
+    for (y, expanding) in rows_to_expand.iter().enumerate() {
+        if !expanding { continue; }
+
+        let mut newline: Vec<char> = Vec::new();
+        for c in grid.g[y+offset].iter() { newline.push(*c); }
+        grid.g.insert(y+offset, newline);
+        offset += 1;
+    }
+
+    offset=0;
+    for (x, expanding) in columns_to_expand.iter().enumerate() {
+        if !expanding { continue; }
+        
+        for (_y, row) in grid.g.iter_mut().enumerate() {
+            row.insert(x + offset, '.');
+        }
+
+        offset += 1;
+    }
+
+    println!("map:");
+    print_map(&grid);
+
+    let mut galaxies: Vec<Coord> = Vec::new();
+    for (y, row) in grid.g.iter().enumerate() {
+        for (x, character) in row.iter().enumerate() {
+            if *character == '#' { galaxies.push(pt(x as i64,y as i64)); }
+        }
+    }
+    println!("galaxy list: {galaxies:?}");
+
+    let mut sum = 0;
+    for a in galaxies.iter() {
+        for b in galaxies.iter() {
+            sum += (b.x-a.x).abs() + (b.y-a.y).abs();
+        }
+    }
+
+    sum = sum / 2;
+
+    println!("behold, this is the sum of sums!: {sum}");
+
+    println!("okay let's do that again for part 2, but differently.");
+
+    let mut grid2 = Grid::<char> { g: Vec::new() };
+    let mut galaxies = Vec::new();
+    let dilation_factor = 999_999;
+    let mut rows_to_expand = Vec::new();
+    let mut columns_to_expand = Vec::new();
+    for _y in contents.lines() {
+        rows_to_expand.push(true);
+    }
+    for _x in contents.lines().nth(0).expect("there's gotta be a first line").chars() {
+        columns_to_expand.push(true);
+    }
+
+    // let's start this over.
+    for (y, line) in contents.lines().enumerate() {
+
+        let mut row = Vec::new();
+        for (x, c) in line.chars().enumerate() {
+            if c == '#' {
+                rows_to_expand[y] = false;
+                columns_to_expand[x] = false;
+                galaxies.push(pt(x as i64,y as i64)); 
+            }
+            row.push(c);
+        }
+        grid2.g.push(row);
+    }
+
+    for g in galaxies.iter_mut() {
+        let mut expansions = 0;
+        for (y, expanding) in rows_to_expand.iter().enumerate() {
+            if !expanding { continue; }
+            if g.y > y as i64 { expansions += dilation_factor; }
+        }
+        g.y += expansions;
+
+        expansions = 0;
+        for (x, expanding) in columns_to_expand.iter().enumerate() {
+            if !expanding { continue; }
+            if g.x > x as i64 { expansions += dilation_factor; }
+        }
+        g.x += expansions;
+    }
+    
+    let mut sum: i128 = 0;
+    for a in galaxies.iter() {
+        for b in galaxies.iter() {
+            sum += ((b.x-a.x).abs() + (b.y-a.y).abs()) as i128;
+        }
+    }
+
+    sum = sum / 2;
+    println!("behold, this is the sum of sums!: {sum}");
+}
+
+fn print_map(grid: &Grid<char>) {
+    for row in grid.g.iter() {
+        let line: Vec<String> = row.iter().map(|x| x.to_string()).collect();
+        let l = line.join("");
+        println!("{l}");
+    }
+}

day11/target/.rustc_info.json

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+{"rustc_fingerprint":11672801278650259402,"outputs":{"15729799797837862367":{"success":true,"status":"","code":0,"stdout":"___\nlib___.rlib\nlib___.dylib\nlib___.dylib\nlib___.a\nlib___.dylib\n/Users/shoofle/.rustup/toolchains/stable-x86_64-apple-darwin\noff\npacked\nunpacked\n___\ndebug_assertions\npanic=\"unwind\"\nproc_macro\ntarget_arch=\"x86_64\"\ntarget_endian=\"little\"\ntarget_env=\"\"\ntarget_family=\"unix\"\ntarget_feature=\"cmpxchg16b\"\ntarget_feature=\"fxsr\"\ntarget_feature=\"sse\"\ntarget_feature=\"sse2\"\ntarget_feature=\"sse3\"\ntarget_feature=\"ssse3\"\ntarget_has_atomic=\"128\"\ntarget_has_atomic=\"16\"\ntarget_has_atomic=\"32\"\ntarget_has_atomic=\"64\"\ntarget_has_atomic=\"8\"\ntarget_has_atomic=\"ptr\"\ntarget_os=\"macos\"\ntarget_pointer_width=\"64\"\ntarget_vendor=\"apple\"\nunix\n","stderr":""},"4614504638168534921":{"success":true,"status":"","code":0,"stdout":"rustc 1.69.0 (84c898d65 2023-04-16)\nbinary: rustc\ncommit-hash: 84c898d65adf2f39a5a98507f1fe0ce10a2b8dbc\ncommit-date: 2023-04-16\nhost: x86_64-apple-darwin\nrelease: 1.69.0\nLLVM version: 15.0.7\n","stderr":""}},"successes":{}}

day11/target/CACHEDIR.TAG

@@ -0,0 +1,3 @@
+Signature: 8a477f597d28d172789f06886806bc55
+# This file is a cache directory tag created by cargo.
+# For information about cache directory tags see https://bford.info/cachedir/

day11/target/debug/.fingerprint/day11-e3eea56213de9d74/bin-day11

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+f609fbbae361eb07

day11/target/debug/.fingerprint/day11-e3eea56213de9d74/bin-day11.json

@@ -0,0 +1 @@
+{"rustc":3659767333214291318,"features":"[]","target":3176960092119891533,"profile":11736316127369858332,"path":1684066648322511884,"deps":[],"local":[{"CheckDepInfo":{"dep_info":"debug/.fingerprint/day11-e3eea56213de9d74/dep-bin-day11"}}],"rustflags":[],"metadata":7797948686568424061,"config":2202906307356721367,"compile_kind":0}

day11/target/debug/.fingerprint/day11-e3eea56213de9d74/invoked.timestamp

@@ -0,0 +1 @@
+This file has an mtime of when this was started.

day11/target/debug/.fingerprint/day11-e3eea56213de9d74/output-bin-day11

@@ -0,0 +1,3 @@
+{"message":"method `get` is never used","code":{"code":"dead_code","explanation":null},"level":"warning","spans":[{"file_name":"src/main.rs","byte_start":238,"byte_end":241,"line_start":12,"line_end":12,"column_start":8,"column_end":11,"is_primary":true,"text":[{"text":"    fn get(&self, r: Coord) -> Option<T> {","highlight_start":8,"highlight_end":11}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"`#[warn(dead_code)]` on by default","code":null,"level":"note","spans":[],"children":[],"rendered":null}],"rendered":"\u001b[0m\u001b[1m\u001b[33mwarning\u001b[0m\u001b[0m\u001b[1m: method `get` is never used\u001b[0m\n\u001b[0m  \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m--> \u001b[0m\u001b[0msrc/main.rs:12:8\u001b[0m\n\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m\n\u001b[0m\u001b[1m\u001b[38;5;12m12\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m\u001b[0m \u001b[0m\u001b[0m    fn get(&self, r: Coord) -> Option<T> {\u001b[0m\n\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m| \u001b[0m\u001b[0m       \u001b[0m\u001b[0m\u001b[1m\u001b[33m^^^\u001b[0m\n\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m\n\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m= \u001b[0m\u001b[0m\u001b[1mnote\u001b[0m\u001b[0m: `#[warn(dead_code)]` on by default\u001b[0m\n\n"}
+{"message":"method `set` is never used","code":{"code":"dead_code","explanation":null},"level":"warning","spans":[{"file_name":"src/main.rs","byte_start":511,"byte_end":514,"line_start":21,"line_end":21,"column_start":8,"column_end":11,"is_primary":true,"text":[{"text":"    fn set(&mut self, r: Coord, value: T) {","highlight_start":8,"highlight_end":11}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[],"rendered":"\u001b[0m\u001b[1m\u001b[33mwarning\u001b[0m\u001b[0m\u001b[1m: method `set` is never used\u001b[0m\n\u001b[0m  \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m--> \u001b[0m\u001b[0msrc/main.rs:21:8\u001b[0m\n\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m\n\u001b[0m\u001b[1m\u001b[38;5;12m21\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m\u001b[0m \u001b[0m\u001b[0m    fn set(&mut self, r: Coord, value: T) {\u001b[0m\n\u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m| \u001b[0m\u001b[0m       \u001b[0m\u001b[0m\u001b[1m\u001b[33m^^^\u001b[0m\n\n"}
+{"message":"2 warnings emitted","code":null,"level":"warning","spans":[],"children":[],"rendered":"\u001b[0m\u001b[1m\u001b[33mwarning\u001b[0m\u001b[0m\u001b[1m: 2 warnings emitted\u001b[0m\n\n"}

day11/target/debug/day11.d

@@ -0,0 +1 @@
+/Users/shoofle/Projects/aoc_2023/day11/target/debug/day11: /Users/shoofle/Projects/aoc_2023/day11/src/main.rs

day11/target/debug/deps/day11-e3eea56213de9d74.d

@@ -0,0 +1,5 @@
+/Users/shoofle/Projects/aoc_2023/day11/target/debug/deps/day11-e3eea56213de9d74: src/main.rs
+
+/Users/shoofle/Projects/aoc_2023/day11/target/debug/deps/day11-e3eea56213de9d74.d: src/main.rs
+
+src/main.rs: