y2024d17p2 test works

test.py

@@ -0,0 +1,26 @@
+# JS sucks
+for line in open('./y2024/resources/17_input.txt'):
+    if line.startswith('Program:'):
+        instructions = list(map(int, line.split(': ')[1].split(',')))
+
+def outFromA(a):
+    interim = (a % 8) ^ 3
+    c = a // (2 ** interim)
+    postC = c ^ 6
+    return (postC ^ (a % 8)) % 8
+
+candidates = [0]
+for i in range(len(instructions) - 1, -1, -1):
+    newCandidates = []
+    # print(f'Instruction: {instructions[i]}, candidates: {candidates}')
+    for c in candidates:
+        for j in range(8):
+            num = (c << 3) + j
+            out = outFromA(num)
+            # print(f'Num: {num}, Out: {out}, Instruction: {instructions[i]}')
+            if out == instructions[i]:
+                newCandidates.append(num)
+    candidates = newCandidates
+
+# print(candidates)
+print(min(candidates))

y2024/src/days/d17.rs

@@ -63,17 +63,22 @@ pub fn process_part2(input: &str) -> u32 {
         .collect_vec()
         .concat();
     let mut a = 0;
-    loop {
-        registers.insert("A", a);
-        let out = exec_program(instructions.clone(), &mut registers);
-        if out == orig {
-            println!("{orig:?}");
-            println!("{out:?}");
-            break;
-        }
-        a += 1;
-    }
+    for idx in 1..=orig.len() {
+        let target = orig[orig.len() - idx..].to_vec();
 
+        let mut new_a = a << 3;
+        loop {
+            registers.insert("A", new_a);
+            let out = exec_program(instructions.clone(), &mut registers);
+            println!("target {target:?}");
+            println!("output {out:?}");
+            if out == target {
+                a = new_a;
+                break;
+            }
+            new_a += 1;
+        }
+    }
     a
 }