Add Rust solutions for days 1-3

Signed-off-by: Alek Ratzloff <alekr@jsausa.com>

day02/Day02.rs

@@ -0,0 +1,68 @@
+use std::io::{self, Read};
+
+type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;
+
+fn get_input_string() -> io::Result<String> {
+    let mut buffer = String::new();
+    io::stdin().read_to_string(&mut buffer)?;
+    Ok(buffer)
+}
+
+fn main() -> Result<()> {
+    let program: Vec<_> = get_input_string()?
+        .trim()
+        .split(",")
+        .filter(|s| !s.is_empty())
+        .map(|n| n.parse::<usize>().unwrap())
+        .collect();
+    part1(&program);
+    part2(&program);
+    Ok(())
+}
+
+fn part1(program: &Vec<usize>) {
+    let data = run_program(12, 2, program.clone());
+    println!("Part 1: {}", data[0]);
+}
+
+fn part2(program: &Vec<usize>) {
+    const GOAL: usize = 19690720;
+    for noun in 0..=99 {
+        for verb in 0..=99 {
+            let data = run_program(noun, verb, program.clone());
+            if data[0] == GOAL {
+                println!("Part 2: noun: {} verb: {} answer: {}", noun, verb, (noun * 100) + verb);
+                return;
+            }
+        }
+    }
+    println!("could not find a solution");
+}
+
+fn run_program(noun: usize, verb: usize, mut program: Vec<usize>) -> Vec<usize> {
+    let mut pc = 0;
+    program[1] = noun;
+    program[2] = verb;
+
+    loop {
+        match program[pc] {
+            op @ 1 | op @ 2 => {
+                let in1 = program[program[pc + 1]];
+                let in2 = program[program[pc + 2]];
+                let out = program[pc + 3];
+
+                let value = if op == 1 {
+                    in1 + in2
+                } else {
+                    in1 * in2
+                };
+                program[out] = value;
+            }
+            99 => break,
+            _ => panic!("bad opcode: {}", program[pc]),
+        }
+        pc += 4;
+    }
+
+    program
+}