1 files changed, 60 insertions, 0 deletions
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..a41a05d
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,60 @@
+use std::fs;
+
+fn read_file(file : &str) -> String {
+    fs::read_to_string(file).unwrap()
+}
+
+fn required_fuel(mass : u32) -> u32 {
+    (mass / 3).saturating_sub(2)
+}
+
+fn required_fuel_with_fuel(mass : u32) -> u32 {
+    let mut total = 0;
+    let mut current = mass;
+    loop {
+        current = required_fuel(current);
+        total += current;
+        if current == 0 {
+            break;
+        }
+    }
+    total
+}
+
+fn day1() {
+    let input = read_file("input1");
+    let sum : u32 = input.split('\n')
+                      .filter(|x| !x.is_empty())
+                      .map(|x| x.parse::<u32>().unwrap())
+                      .map(|x| required_fuel(x))
+                      .sum();
+    println!("1a: {}", sum);
+
+    let sum2 : u32 = input.split('\n')
+                         .filter(|x| !x.is_empty())
+                         .map(|x| x.parse::<u32>().unwrap())
+                         .map(|x| required_fuel_with_fuel(x))
+                         .sum();
+    println!("1b: {}", sum2);
+}
+
+fn main() {
+    day1();
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_day1() {
+        assert_eq!(required_fuel(12), 2);
+        assert_eq!(required_fuel(14), 2);
+        assert_eq!(required_fuel(1969), 654);
+        assert_eq!(required_fuel(100756), 33583);
+
+        assert_eq!(required_fuel_with_fuel(14), 2);
+        assert_eq!(required_fuel_with_fuel(1969), 966);
+        assert_eq!(required_fuel_with_fuel(100756), 50346);
+    }
+}