day 1 solution in rust

2022/.gitignore

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+target

2022/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "anyhow"
+version = "1.0.66"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "216261ddc8289130e551ddcd5ce8a064710c0d064a4d2895c67151c92b5443f6"
+
+[[package]]
+name = "aoc2022"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+]

2022/Cargo.toml

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+[package]
+name = "aoc2022"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0.66"

2022/src/days/day1.rs

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+use anyhow::Result;
+use std::fs;
+
+pub fn run() -> Result<()> {
+    let file_contents = fs::read_to_string("day1.txt")?;
+    let lines = file_contents.lines();
+    let mut calories = Vec::with_capacity(lines.clone().count());
+    let mut count: u32 = 0;
+
+    for line in lines {
+        if line.is_empty() {
+            calories.push(count);
+            count = 0;
+        } else {
+            count += line.parse::<u32>().expect("not a number");
+        }
+    }
+
+    let max = calories.iter().max().expect("Should have been a number");
+    println!("Maximum calories is {}", max);
+
+    let mut sorted_calories = calories.clone();
+    sorted_calories.sort_by(|a, b| b.cmp(a));
+    let top_three: u32 = sorted_calories.get(0..3).expect("Not able to be sorted").iter().sum();
+    println!("Top 3 calories {}", top_three);
+    Ok(())
+}

2022/src/days/mod.rs

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+pub mod day1;

2022/src/main.rs

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+use anyhow::{anyhow, Result};
+use std::env;
+
+mod days;
+
+fn help() {
+    println!("Usage: {} <day-number>", env!("CARGO_BIN_NAME"));
+}
+
+fn run_day(number: i32) -> Result<()> {
+    match number {
+        1 => {
+            days::day1::run()?;
+        }
+        _ => return Err(anyhow!("Invalid day provided")),
+    }
+    Ok(())
+}
+
+fn main() -> Result<()> {
+    let args: Vec<String> = env::args().collect();
+
+    match args.len() {
+        2 => {
+            let number: i32 = match args[1].parse() {
+                Ok(n) => n,
+                Err(_) => {
+                    help();
+                    return Err(anyhow!("Argument is not an integer"));
+                }
+            };
+            run_day(number)?;
+        }
+        _ => {
+            help();
+            return Err(anyhow!("Invalid arguments provided"));
+        }
+    }
+
+    Ok(())
+}