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use std::io::{self, BufRead};
use std::env;
// https://stackoverflow.com/q/37888042/remove-single-trailing-newline-from-string-without-cloning
fn trim_newline(s: &mut String) {
if s.ends_with('\n') {
s.pop();
if s.ends_with('\r') {
s.pop();
}
}
}
fn read_input() -> Vec<usize> {
let stdin = io::stdin();
// Far from neat, but gets the job done...
stdin.lock().split(b',').map(|v| {
let mut s = String::from_utf8(v.unwrap()).unwrap();
trim_newline(&mut s);
let u:u32 = s.parse().unwrap();
u as usize
}).collect()
}
fn restore_gravity_assist(window:&mut [usize], noun:usize, verb:usize) {
window[0] = noun;
window[1] = verb;
}
fn add(ip:usize, memory:&mut Vec<usize>) {
let result = memory[ip + 3];
let left = memory[ip + 1];
let right = memory[ip + 2];
memory[result] = memory[left] + memory[right];
}
fn mul(ip:usize, memory:&mut Vec<usize>) {
let result = memory[ip + 3];
let left = memory[ip + 1];
let right = memory[ip + 2];
memory[result] = memory[left] * memory[right];
}
fn intcode(mut memory:Vec<usize>) -> usize {
let mut ip = 0;
while ip < memory.len() {
let op = memory[ip];
match op {
1 => { add(ip, &mut memory); ip += 4 },
2 => { mul(ip, &mut memory); ip += 4 },
99 => break,
op => panic!("Invalid operation {}", op),
}
}
memory[0]
}
fn first_puzzle(mut memory:Vec<usize>) -> usize {
println!("No argument provided, hence attemping to solve first puzzle.");
restore_gravity_assist(&mut memory[1..3], 12, 2);
intcode(memory)
}
fn second_puzzle(desired:usize, mut memory:Vec<usize>) -> Option<usize> {
println!("Desired output {} specified. Assuming second puzzle to search for it.", desired);
for noun in 0..100 {
for verb in 0..100 {
restore_gravity_assist(&mut memory[1..3], noun, verb);
if intcode(memory.clone()) == desired {
return Some(100 * noun + verb);
}
}
}
None
}
fn main() {
let memory = read_input();
let needle = env::args().nth(1);
let solution = match needle {
None => Some(first_puzzle(memory)),
Some(n) => second_puzzle(n.parse().unwrap_or(0), memory),
};
match solution {
Some(s) => println!("Solution: {}.", s),
_ => println!("No solution found."),
}
}
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