Day 1 solution in Rust

I have no idea what I'm doing in Rust, and I definitely don't understand
borrowing yet, so this is a hideous solution on multiple fronts. I'm not
sure that I'll be sticking with Rust as AoC doesn't feel like a
conducive environment to learn it in.

.gitignore

@@ -0,0 +1 @@
+/target

.vscode/launch.json

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+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "lldb",
+            "request": "launch",
+            "name": "Debug executable 'aoc2021'",
+            "cargo": {
+                "args": [
+                    "build",
+                    "--bin=aoc2021",
+                    "--package=aoc2021"
+                ],
+                "filter": {
+                    "name": "aoc2021",
+                    "kind": "bin"
+                }
+            },
+            "args": [],
+            "cwd": "${workspaceFolder}"
+        },
+        {
+            "type": "lldb",
+            "request": "launch",
+            "name": "Debug unit tests in executable 'aoc2021'",
+            "cargo": {
+                "args": [
+                    "test",
+                    "--no-run",
+                    "--bin=aoc2021",
+                    "--package=aoc2021"
+                ],
+                "filter": {
+                    "name": "aoc2021",
+                    "kind": "bin"
+                }
+            },
+            "args": [],
+            "cwd": "${workspaceFolder}"
+        }
+    ]
+}

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "aoc2021"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "aoc2021"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/main.rs

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+use std::io::{self, BufRead};
+use std::fs::File;
+use std::path::Path;
+
+fn main() {
+    if let Ok(lines) = read_lines("inputs/01.txt") {
+        part1(lines);
+    }
+    if let Ok(lines) = read_lines("inputs/01.txt") {
+        part2(lines);
+    }
+}
+
+fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
+where P: AsRef<Path>, {
+    let file = File::open(filename)?;
+    Ok(io::BufReader::new(file).lines())
+}
+
+fn part1(lines: io::Lines<io::BufReader<File>>) {
+    let mut last_depth: i64 = 0;
+    let mut num_increased = -1;
+
+    for line in lines {
+        if let Ok(depth) = line {
+            let di: i64 = depth.parse().unwrap();
+            if di > last_depth {
+                num_increased = num_increased + 1;
+            }
+            last_depth = di;
+        }
+    }
+
+    println!("part1: increased: {:?}", num_increased);
+}
+
+fn part2(lines: io::Lines<io::BufReader<File>>) {
+    let mut last_total: i64 = 0;
+    let mut num_increased = -1;
+    let mut num1;
+    let mut num2 = -1;
+    let mut num3 = -1;
+
+    for line in lines {
+        if let Ok(depth) = line {
+            let di: i64 = depth.parse().unwrap();
+            num1 = num2;
+            num2 = num3;
+            num3 = di;
+            if num1 < 0 || num2 < 0 || num3 < 0 {
+                continue
+            }
+
+            let total = num1 + num2 + num3;
+            if total > last_total {
+                num_increased = num_increased + 1;
+            }
+            last_total = total;
+        }
+    }
+
+    println!("part2: increased: {:?}", num_increased);
+}