2024.09

challenges/2024/09-diskFragmenter/README.md

@@ -0,0 +1,5 @@
+# [Day 9: Disk Fragmenter](https://adventofcode.com/2024/day/9)
+
+Part 2 is:
+* less than 6277851188082
+            6272188244509

challenges/2024/09-diskFragmenter/main.py

@@ -0,0 +1,129 @@
+import sys
+from collections import namedtuple, defaultdict
+
+
+Segment = namedtuple("Segment", ["id", "len"])
+
+
+def parse(instr: str) -> list[Segment]:
+    res = []
+    next_id = 0
+    
+    for i, v in enumerate(instr):
+        v = int(v)
+        if i % 2 == 0:
+            # this is a file
+            res.append(Segment(next_id, v))
+            next_id += 1
+        else:
+            # this is a gap
+            res.append(Segment(None, v))
+            
+    if res[-1].id is None:
+        # random gap at the end? no thanks
+        res = res[:-1]
+            
+    return res
+
+
+def calc_checksum(files: list[Segment]) -> int:
+    acc = 0
+    pos = 0
+    for file in files:
+        if file.id is not None:
+            # sum of sequence of n consecutive integers is (n / 2)(first + last)
+            acc += int((file.len / 2) * ((pos * 2) + file.len - 1) * file.id)
+        pos += file.len
+    return acc
+
+
+def one(instr: str):
+    files = parse(instr)
+        
+    i = 0
+    while i < len(files) - 1:        
+        f = files[i]
+        last_file = files[-1]
+        
+        if last_file.id is None:
+            files = files[:-1]
+            continue
+        
+        if f.id is None:
+            # _debug(i, files[i])
+            last_file = files[-1]
+            
+            assert last_file.id is not None
+            if last_file.len > f.len:
+                files[-1] = Segment(last_file.id, last_file.len - f.len)
+                files[i] = Segment(last_file.id, f.len)
+            elif last_file.len == f.len:
+                # we're gonna move all of this so just delete it
+                files = files[:-1]
+                files[i] = last_file
+            else:
+                # TODO: when we haven't got enough in this last file so we need to split f into two
+                files = files[:-1]
+                files[i] = last_file
+                assert f.len - last_file.len != 0
+                files.insert(i+1, Segment(None, f.len - last_file.len))            
+        
+        i += 1
+    
+    return calc_checksum(files)
+
+
+def two(instr: str):
+    files = parse(instr)
+    
+    gaps = defaultdict(list)
+    
+    for i, file in enumerate(files):
+        if file.id is None and file.len != 0:
+            gaps[file.len].append(i)
+            
+    moved = set()
+    
+    i = len(files) - 1
+    while i > 0:
+        f = files[i]
+        
+        if f.id is not None and f.id not in moved:
+            gap_loc = None
+            for j, v in enumerate(files):
+                if j >= i:
+                    break
+                
+                if v.id is None and v.len >= f.len:
+                    gap_loc = j
+                    break
+                    
+            if gap_loc is not None:
+                v = files[gap_loc]
+                if v.len == f.len:
+                    files[i], files[gap_loc] = files[gap_loc], files[i]
+                else:
+                    files[i] = Segment(None, f.len)
+                    files[gap_loc] = f
+                    files.insert(gap_loc + 1, Segment(None, v.len - f.len))
+                moved.add(f.id)
+                
+        i -= 1
+        
+    return calc_checksum(files)
+
+
+def _debug(*args, **kwargs):
+    kwargs["file"] = sys.stderr
+    print(*args, **kwargs)
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2 or sys.argv[1] not in ["1", "2"]:
+        print("Missing day argument", file=sys.stderr)
+        sys.exit(1)
+    inp = sys.stdin.read().strip()
+    if sys.argv[1] == "1":
+        print(one(inp))
+    else:
+        print(two(inp))

challenges/2024/09-diskFragmenter/tests.json

@@ -0,0 +1,14 @@
+{
+    "1": [
+        {
+            "is": "1928",
+            "input": "2333133121414131402\n"
+        }
+    ],
+    "2": [
+        {
+            "is": "2858",
+            "input": "2333133121414131402\n"
+        }
+    ]
+}

challenges/2024/README.md

@@ -22,3 +22,4 @@ A day denoted with an asterisk means it has a visualisation.
 | 06 - Guard Gallivant                | ★ ★   | Python               | oh dear runtime (also I knew what I wanted to do for so long it just took me 3 hours to implement it properly) |
 | 07 - Bridge Repair                  | ★ ★   | Python               | Maths? Backwards?? |
 | 08* - Resonant Collinearity         | ★ ★   | Python               | `Fraction` saving us all from the curse of a computer's inability to do floating point arithmetic |
+| 09 - Disk Fragmenter                | ★ ★   | Python               | Many cursed strategies were attempted before I landed on the final implementation |

challenges/2024/benchmarks.jsonl

@@ -14,3 +14,5 @@
 {"day": 7, "part": 2, "runner": "py", "min": 0.02680826187133789, "max": 0.04485297203063965, "avg": 0.029925800323486327, "n": 500}
 {"day": 8, "part": 1, "runner": "py", "min": 0.025803089141845703, "max": 0.036757469177246094, "avg": 0.02743640899658203, "n": 200}
 {"day": 8, "part": 2, "runner": "py", "min": 0.027710437774658203, "max": 0.035851240158081055, "avg": 0.029560294151306152, "n": 200}
+{"day": 9, "part": 1, "runner": "py", "min": 0.5576984882354736, "max": 0.5812969207763672, "avg": 0.5654887676239013, "n": 5}
+{"day": 9, "part": 2, "runner": "py", "min": 3.876859188079834, "max": 4.176096677780151, "avg": 4.0687650680542, "n": 5}