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Day 2 part 2

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Wesley Moore 2019-12-02 21:45:25 +11:00
parent 756c29ad71
commit d80911a0cf
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1 changed files with 35 additions and 8 deletions
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43
2019/src/bin/day2.rs
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@ -4,20 +4,32 @@ use advent_of_code::input;
fn main() -> io::Result<()> { fn main() -> io::Result<()> {
let input = fs::read_to_string("input/day2.txt")?; let input = fs::read_to_string("input/day2.txt")?;
let mut program = input::read_separated_line(',', &input)?; let program = input::read_separated_line(',', &input)?;
// To do this, before running the program, replace position 1 with the value 12 and replace // To do this, before running the program, replace position 1 with the value 12 and replace
// position 2 with the value 2. What value is left at position 0 after the program halts? // position 2 with the value 2. What value is left at position 0 after the program halts?
program[1] = 12; let mut part1 = program.clone();
program[2] = 2; run_program(&mut part1, 12, 2);
run_program(&mut program);
println!("Part 1: {}", program[0]); println!("Part 1: {}", part1[0]);
// Part 2
// Determine what pair of inputs produces the output 19690720."
// Each of the two input values will be between 0 and 99, inclusive
let (noun, verb) = part2(19690720, &program);
println!(
"Part 2: noun={} verb={} result={}",
noun,
verb,
100 * noun + verb
);
Ok(()) Ok(())
} }
fn run_program(program: &mut [i32]) { fn run_program(program: &mut [i32], noun: i32, verb: i32) {
program[1] = noun;
program[2] = verb;
let mut addr = 0; let mut addr = 0;
loop { loop {
@ -38,6 +50,21 @@ fn run_program(program: &mut [i32]) {
} }
} }
fn part2(target: i32, program: &[i32]) -> (i32, i32) {
for noun in 0..=99 {
for verb in 0..=99 {
let mut candidate = program.to_vec();
run_program(&mut candidate, noun, verb);
if candidate[0] == target {
return (noun, verb);
}
}
}
panic!("Did not find solution");
}
#[cfg(test)] #[cfg(test)]
mod tests { mod tests {
use super::*; use super::*;
@ -47,7 +74,7 @@ mod tests {
let input = "1,0,0,0,99"; let input = "1,0,0,0,99";
let mut program = input::read_separated_line(',', &input).unwrap(); let mut program = input::read_separated_line(',', &input).unwrap();
run_program(&mut program); run_program(&mut program, 0, 0);
assert_eq!(program, &[2, 0, 0, 0, 99]) assert_eq!(program, &[2, 0, 0, 0, 99])
} }
@ -56,7 +83,7 @@ mod tests {
let input = "1,1,1,4,99,5,6,0,99"; let input = "1,1,1,4,99,5,6,0,99";
let mut program = input::read_separated_line(',', &input).unwrap(); let mut program = input::read_separated_line(',', &input).unwrap();
run_program(&mut program); run_program(&mut program, 1, 1);
assert_eq!(program, &[30, 1, 1, 4, 2, 5, 6, 0, 99]) assert_eq!(program, &[30, 1, 1, 4, 2, 5, 6, 0, 99])
} }