day1: add rust impl, example data

.gitignore

@@ -24,3 +24,5 @@ docs/site/
 # environment.
 Manifest.toml
 
+target
+Cargo.lock

day1/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day1"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day1/example.txt

@@ -0,0 +1,14 @@
+1000
+2000
+3000
+
+4000
+
+5000
+6000
+
+7000
+8000
+9000
+
+10000

day1/src/main.rs

@@ -0,0 +1,62 @@
+// From rust by example
+
+use std::fs::File;
+use std::io::{self, BufRead};
+use std::path::Path;
+
+fn aoc_day1(path : &str, n : i64) -> i64 {
+    let mut max_calories : [i64; 3] = [0, 0, 0];
+    let mut calories : i64 = 0;
+    if let Ok(lines) = read_lines(path) {
+        for line in lines {
+            if let Ok(scalories) = line {
+                println!("{}", scalories);
+                println!("[{}, {}, {}]", max_calories[0], max_calories[1], max_calories[2]);
+                if scalories.len() == 0 {
+                    if calories > max_calories[0] {
+                        max_calories[0] = calories;
+                        max_calories.sort();
+                    }
+                    calories = 0;
+                } else {
+                    let snack_calories = scalories.parse::<i64>().unwrap();
+                    calories += snack_calories;
+                }
+            }
+        }
+        // eof
+        if calories > max_calories[0] {
+            max_calories[0] = calories;
+            max_calories.sort();
+        }
+    }
+    if n == 1 {
+        return max_calories[2];
+    } else {
+        return max_calories.iter().sum();
+    }
+}
+
+// The output is wrapped in a Result to allow matching on errors
+// Returns an Iterator to the Reader of the lines of the file.
+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 main() {
+    aoc_day1("day1input.txt", 1);
+}
+
+#[test]
+fn day1input() {
+    assert_eq!(aoc_day1("day1input.txt", 1), 69206);
+    assert_eq!(aoc_day1("day1input.txt", 3), 197400);
+}
+
+#[test]
+fn example() {
+    assert_eq!(aoc_day1("example.txt", 1), 24000);
+    assert_eq!(aoc_day1("example.txt", 3), 45000);
+}