2019: day02: part 1

aoc2019/src/day02.rs

@@ -0,0 +1,82 @@
+use aoc::err;
+use aoc::Result;
+
+const INPUT: &str = include_str!("../input/day02.txt");
+
+fn parse_intcode(input: &str) -> Result<Vec<usize>> {
+    input
+        .trim_end()
+        .split(',')
+        .map(|x| x.parse().map_err(|e| err!("couldn't parse int: {}", e)))
+        .collect()
+}
+
+pub fn run() -> Result<()> {
+    let intcode = parse_intcode(INPUT)?;
+    println!("part 1: {}", part1(&mut intcode.clone())?);
+
+    Ok(())
+}
+
+fn eval(intcode: &mut [usize]) -> Result<()> {
+    let mut pc = 0;
+
+    while intcode[pc] != 99 {
+        let op1 = intcode[pc + 1];
+        let op2 = intcode[pc + 2];
+        let res = intcode[pc + 3];
+
+        match intcode[pc] {
+            1 => intcode[res] = intcode[op1] + intcode[op2],
+            2 => intcode[res] = intcode[op1] * intcode[op2],
+            _ => return Err(err!("unknown opcode: {}", intcode[pc])),
+        };
+
+        pc += 4;
+    }
+
+    Ok(())
+}
+
+fn part1(input: &mut Vec<usize>) -> Result<usize> {
+    input[1] = 12;
+    input[2] = 2;
+
+    eval(input)?;
+
+    Ok(input[0])
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_provided() {
+        let mut intcode = parse_intcode("1,9,10,3,2,3,11,0,99,30,40,50").unwrap();
+        eval(&mut intcode).unwrap();
+        assert_eq!(intcode, &[3500, 9, 10, 70, 2, 3, 11, 0, 99, 30, 40, 50]);
+
+        let mut intcode = parse_intcode("1,0,0,0,99").unwrap();
+        eval(&mut intcode).unwrap();
+        assert_eq!(intcode, &[2, 0, 0, 0, 99]);
+
+        let mut intcode = parse_intcode("2,3,0,3,99").unwrap();
+        eval(&mut intcode).unwrap();
+        assert_eq!(intcode, &[2, 3, 0, 6, 99]);
+
+        let mut intcode = parse_intcode("2,4,4,5,99,0").unwrap();
+        eval(&mut intcode).unwrap();
+        assert_eq!(intcode, &[2, 4, 4, 5, 99, 9801]);
+
+        let mut intcode = parse_intcode("1,1,1,4,99,5,6,0,99").unwrap();
+        eval(&mut intcode).unwrap();
+        assert_eq!(intcode, &[30, 1, 1, 4, 2, 5, 6, 0, 99]);
+    }
+
+    #[test]
+    fn part1_real() {
+        let mut intcode = parse_intcode(INPUT).unwrap();
+        assert_eq!(part1(&mut intcode).unwrap(), 6568671);
+    }
+}

aoc2019/src/lib.rs

@@ -1,4 +1,5 @@
 pub mod day01;
+pub mod day02;
 
 pub type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;
 

aoc2019/src/main.rs

@@ -1,11 +1,12 @@
 use std::env;
 
 use aoc2019::day01;
+use aoc2019::day02;
 
 use aoc2019::Result;
 
 fn main() -> Result<()> {
-    let days: &[fn() -> Result<()>] = &[day01::run];
+    let days: &[fn() -> Result<()>] = &[day01::run, day02::run];
 
     let mut args = env::args();
     args.next();