day 7 DONE

day06/src/main.rs

@@ -124,15 +124,15 @@ fn patrol_and_count_potential_loops(start: Coord, lab: &HashMap<Coord, char>) ->
             None => break,
         }
     }
+    println!("{}",candidates.len());
 
     let mut loop_spots: HashSet<Coord> = HashSet::new();
     for candidate_location in candidates {
-        let mut dream_lab = lab.clone();
-        
-        if dream_lab.get(&candidate_location) != Some(&'.') {
+        if lab.get(&candidate_location) != Some(&'.') {
             continue;
         }
 
+        let mut dream_lab = lab.clone();
         dream_lab.insert(candidate_location, '#');
 
         if let Ok(_) = patrol(start, &dream_lab){

day07/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "day07"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

day07/src/main.rs

@@ -0,0 +1,72 @@
+use std::fs;
+use std::env;
+
+fn main() {
+    println!("Hello, AoC day 07!");
+
+    let args: Vec<String> = env::args().collect();
+    if args.len() != 2 {
+        println!("wrong number of arguments!");
+        std::process::exit(1);
+    }
+
+    let file_path = &args[1];
+
+    let contents = fs::read_to_string(file_path).expect("Should have been able to read the file");
+
+    let mut sum_a: i128 = 0;
+    let mut sum_b: i128 = 0;
+    for line in contents.lines() {
+        let (target_string, many_string) = line.split_once(":").expect("found a bad line w/o :");
+        let (target, many): (i128, Vec<i128>) = (
+            target_string.parse().expect("bad int"), 
+            many_string.trim().split(" ").map(|s| s.parse::<i128>().expect(&format!("bad int: {s}"))).collect()
+            );
+
+        for x in 0..(1 << many.len()) {
+            if target == equation_result_a(&many, x) {
+                sum_a += target;
+                break;
+            }
+        }
+
+        for x in 0..(1 << (many.len()*2)) {
+            if target == equation_result_b(&many, x) {
+                sum_b += target;
+                break;
+            }
+        }
+    }
+
+    println!("sum of valid targets is {sum_a}, part b is {sum_b}");
+}
+
+fn equation_result_a(numbers: &[i128], bitmask: usize) -> i128 {
+    let mut sum = numbers[0];
+    for i in 1..numbers.len() {
+        sum = match (bitmask >> (i-1)) & 1 {
+            0 => sum + numbers[i],
+            1 => sum * numbers[i],
+            _ => panic!("how did this happen"),
+        }
+    }
+    return sum;
+}
+
+fn equation_result_b(numbers: &[i128], bitmask: usize) -> i128 {
+    let mut sum = numbers[0];
+    for i in 1..numbers.len() {
+        sum = match (bitmask >> ((i-1)*2)) & 0b11 {
+            0 => sum + numbers[i],
+            1 => sum * numbers[i],
+            2 => concatenate(sum, numbers[i]),
+            3 => { return -1; },
+            _ => panic!("how did this happen"),
+        }
+    }
+    return sum;
+}
+
+fn concatenate(a: i128, b: i128) -> i128 {
+    return (a * (10_i128).pow(b.ilog10()+1)) + b;
+}